diff --git a/exercises/00_hello_world/main.cpp b/exercises/00_hello_world/main.cpp
index 8866f3c15..fa454e132 100644
--- a/exercises/00_hello_world/main.cpp
+++ b/exercises/00_hello_world/main.cpp
@@ -6,6 +6,6 @@
 
 int main(int argc, char **argv) {
     // TODO: 在控制台输出 "Hello, InfiniTensor!" 并换行
-    std::cout : "Hello, InfiniTensor!" + std::endl;
+    std::cout << "Hello, InfiniTensor!" << std::endl;
     return 0;
 }
diff --git a/exercises/01_variable&add/main.cpp b/exercises/01_variable&add/main.cpp
index 5014863fd..fb05c57f3 100644
--- a/exercises/01_variable&add/main.cpp
+++ b/exercises/01_variable&add/main.cpp
@@ -5,6 +5,7 @@
 int main(int argc, char **argv) {
     // TODO: 补全变量定义并打印加法运算
     // x ?
+    int x = 10;
     std::cout << x << " + " << x << " = " << x + x << std::endl;
     return 0;
 }
diff --git a/exercises/02_function/main.cpp b/exercises/02_function/main.cpp
index b5eef7f28..2bde9960f 100644
--- a/exercises/02_function/main.cpp
+++ b/exercises/02_function/main.cpp
@@ -5,7 +5,7 @@
 // NOTICE: 补充由内而外读法的机翻解释 <https://learn.microsoft.com/zh-cn/cpp/c-language/interpreting-more-complex-declarators?view=msvc-170>
 
 // TODO: 在这里声明函数
-
+int add(int a, int b);
 int main(int argc, char **argv) {
     ASSERT(add(123, 456) == 123 + 456, "add(123, 456) should be 123 + 456");
 
@@ -16,4 +16,5 @@ int main(int argc, char **argv) {
 
 int add(int a, int b) {
     // TODO: 补全函数定义，但不要移动代码行
+    return a + b;
 }
diff --git a/exercises/03_argument&parameter/main.cpp b/exercises/03_argument&parameter/main.cpp
index 7fb5d3c2f..76136eae6 100644
--- a/exercises/03_argument&parameter/main.cpp
+++ b/exercises/03_argument&parameter/main.cpp
@@ -8,19 +8,19 @@ void func(int);
 // TODO: 为下列 ASSERT 填写正确的值
 int main(int argc, char **argv) {
     auto arg = 99;
-    ASSERT(arg == ?, "arg should be ?");
+    ASSERT(arg == 99, "arg should be ?");
     std::cout << "befor func call: " << arg << std::endl;
     func(arg);
-    ASSERT(arg == ?, "arg should be ?");
+    ASSERT(arg == 99, "arg should be ?");
     std::cout << "after func call: " << arg << std::endl;
     return 0;
 }
 
 // TODO: 为下列 ASSERT 填写正确的值
 void func(int param) {
-    ASSERT(param == ?, "param should be ?");
+    ASSERT(param == 99, "param should be ?");
     std::cout << "befor add: " << param << std::endl;
     param += 1;
-    ASSERT(param == ?, "param should be ?");
+    ASSERT(param == 100, "param should be ?");
     std::cout << "after add: " << param << std::endl;
 }
diff --git a/exercises/04_static/main.cpp b/exercises/04_static/main.cpp
index f107762fa..32bcb635e 100644
--- a/exercises/04_static/main.cpp
+++ b/exercises/04_static/main.cpp
@@ -2,6 +2,10 @@
 
 // READ: `static` 关键字 <https://zh.cppreference.com/w/cpp/language/storage_duration>
 // THINK: 这个函数的两个 `static` 各自的作用是什么？
+
+// ANSWER：
+// - 第一个 static 用来修饰函数，使得 func 仅在当前的翻译单元可见
+// - 第二个 static 用来修饰局部变量，改变了变量的生命周期，在程序开始时创建，在程序结束时销毁。仅在第一次执行时，被初始化
 static int func(int param) {
     static int static_ = param;
     // std::cout << "static_ = " << static_ << std::endl;
@@ -10,10 +14,10 @@ static int func(int param) {
 
 int main(int argc, char **argv) {
     // TODO: 将下列 `?` 替换为正确的数字
-    ASSERT(func(5) == ?, "static variable value incorrect");
-    ASSERT(func(4) == ?, "static variable value incorrect");
-    ASSERT(func(3) == ?, "static variable value incorrect");
-    ASSERT(func(2) == ?, "static variable value incorrect");
-    ASSERT(func(1) == ?, "static variable value incorrect");
+    ASSERT(func(5) == 5, "static variable value incorrect");
+    ASSERT(func(4) == 6, "static variable value incorrect");
+    ASSERT(func(3) == 7, "static variable value incorrect");
+    ASSERT(func(2) == 8, "static variable value incorrect");
+    ASSERT(func(1) == 9, "static variable value incorrect");
     return 0;
 }
diff --git a/exercises/05_constexpr/main.cpp b/exercises/05_constexpr/main.cpp
index d1db6c9d8..e2cb67092 100644
--- a/exercises/05_constexpr/main.cpp
+++ b/exercises/05_constexpr/main.cpp
@@ -18,7 +18,7 @@ int main(int argc, char **argv) {
 
     // TODO: 观察错误信息，修改一处，使代码编译运行
     // PS: 编译运行，但是不一定能算出结果……
-    constexpr auto ANS_N = 90;
+    constexpr auto ANS_N = 20;
     constexpr auto ANS = fibonacci(ANS_N);
     std::cout << "fibonacci(" << ANS_N << ") = " << ANS << std::endl;
 
diff --git a/exercises/06_array/main.cpp b/exercises/06_array/main.cpp
index 61ed99ec0..bbce324cf 100644
--- a/exercises/06_array/main.cpp
+++ b/exercises/06_array/main.cpp
@@ -11,13 +11,13 @@ unsigned long long fibonacci(int i) {
             return 1;
         default:
             // TODO: 补全三目表达式缺失的部分
-            return <condition> ? <cache> : (arr[i] = fibonacci(i - 1) + fibonacci(i - 2));
+            return arr[i] ? arr[i] : (arr[i] = fibonacci(i - 1) + fibonacci(i - 2));
     }
 }
 
 int main(int argc, char **argv) {
     // TODO: 为此 ASSERT 填写正确的值
-    ASSERT(sizeof(arr) == ?, "sizeof array is size of all its elements");
+    ASSERT(sizeof(arr) == 720, "sizeof array is size of all its elements");
     // ---- 不要修改以下代码 ----
     ASSERT(fibonacci(2) == 1, "fibonacci(2) should be 1");
     ASSERT(fibonacci(20) == 6765, "fibonacci(20) should be 6765");
diff --git a/exercises/07_loop/main.cpp b/exercises/07_loop/main.cpp
index 44fd835cd..d0ca39298 100644
--- a/exercises/07_loop/main.cpp
+++ b/exercises/07_loop/main.cpp
@@ -5,9 +5,9 @@
 // READ: 纯函数 <https://zh.wikipedia.org/wiki/%E7%BA%AF%E5%87%BD%E6%95%B0>
 static unsigned long long fibonacci(int i) {
     // TODO: 为缓存设置正确的初始值
-    static unsigned long long cache[96], cached;
+    static unsigned long long cache[96]{0, 1}, cached = 2;
     // TODO: 设置正确的循环条件
-    for (; false; ++cached) {
+    for (; cached <= i; ++cached) {
         cache[cached] = cache[cached - 1] + cache[cached - 2];
     }
     return cache[i];
diff --git a/exercises/08_pointer/main.cpp b/exercises/08_pointer/main.cpp
index ba37173f5..5e23176f3 100644
--- a/exercises/08_pointer/main.cpp
+++ b/exercises/08_pointer/main.cpp
@@ -5,6 +5,21 @@ bool is_fibonacci(int *ptr, int len, int stride) {
     ASSERT(len >= 3, "`len` should be at least 3");
     // TODO: 编写代码判断从 ptr 开始，每 stride 个元素取 1 个元素，组成长度为 n 的数列是否满足
     // arr[i + 2] = arr[i] + arr[i + 1]
+
+    int n = len;
+
+    int *arr = (int *) malloc(sizeof(int) * n);
+    for (int i = 0; i < n; i ++) {
+        arr[i] = ptr[i * stride];
+    }
+
+    for (int i = 0; i + 2 < n; i++) {
+        if (arr[i + 2] != arr[i] + arr[i + 1]) {
+            free(arr);
+            return false;
+        }
+    }
+    free(arr);
     return true;
 }
 
diff --git a/exercises/09_enum&union/main.cpp b/exercises/09_enum&union/main.cpp
index 3f2cec768..5779dd314 100644
--- a/exercises/09_enum&union/main.cpp
+++ b/exercises/09_enum&union/main.cpp
@@ -37,6 +37,7 @@ ColorEnum convert_by_pun(Color c) {
 
     TypePun pun;
     // TODO: 补全类型双关转换
+    pun.c = c;
 
     return pun.e;
 }
diff --git a/exercises/10_trivial/main.cpp b/exercises/10_trivial/main.cpp
index 6ba23e48e..7706c298b 100644
--- a/exercises/10_trivial/main.cpp
+++ b/exercises/10_trivial/main.cpp
@@ -9,8 +9,9 @@ struct FibonacciCache {
 
 // TODO: 实现正确的缓存优化斐波那契计算
 static unsigned long long fibonacci(FibonacciCache &cache, int i) {
-    for (; false; ++cached) {
-        cache[cached] = cache[cached - 1] + cache[cached - 2];
+    auto &cached = cache.cached;
+    for (; cached <= i; ++cached) {
+        cache.cache[cached] = cache.cache[cached - 1] + cache.cache[cached - 2];
     }
     return cache.cache[i];
 }
@@ -19,7 +20,7 @@ int main(int argc, char **argv) {
     // TODO: 初始化缓存结构体，使计算正确
     // NOTICE: C/C++ 中，读取未初始化的变量（包括结构体变量）是未定义行为
     // READ: 初始化的各种写法 <https://zh.cppreference.com/w/cpp/language/initialization>
-    FibonacciCache fib;
+    FibonacciCache fib{{0, 1}, 2};
     ASSERT(fibonacci(fib, 10) == 55, "fibonacci(10) should be 55");
     std::cout << "fibonacci(10) = " << fibonacci(fib, 10) << std::endl;
     return 0;
diff --git a/exercises/11_method/main.cpp b/exercises/11_method/main.cpp
index 0e08e0a36..eab225933 100644
--- a/exercises/11_method/main.cpp
+++ b/exercises/11_method/main.cpp
@@ -6,7 +6,7 @@ struct Fibonacci {
 
     // TODO: 实现正确的缓存优化斐波那契计算
     unsigned long long get(int i) {
-        for (; false; ++cached) {
+        for (; cached <= i; ++cached) {
             cache[cached] = cache[cached - 1] + cache[cached - 2];
         }
         return cache[i];
@@ -15,7 +15,7 @@ struct Fibonacci {
 
 int main(int argc, char **argv) {
     // TODO: 初始化缓存结构体，使计算正确
-    Fibonacci fib;
+    Fibonacci fib{{0, 1}, 2};
     ASSERT(fib.get(10) == 55, "fibonacci(10) should be 55");
     std::cout << "fibonacci(10) = " << fib.get(10) << std::endl;
     return 0;
diff --git a/exercises/12_method_const/main.cpp b/exercises/12_method_const/main.cpp
index 5521be4da..1eb888aaf 100644
--- a/exercises/12_method_const/main.cpp
+++ b/exercises/12_method_const/main.cpp
@@ -5,7 +5,8 @@
 struct Fibonacci {
     int numbers[11];
     // TODO: 修改方法签名和实现，使测试通过
-    int get(int i) {
+    constexpr int get(int i) const {
+      return numbers[i];
     }
 };
 
diff --git a/exercises/13_class/main.cpp b/exercises/13_class/main.cpp
index 9afa98c5b..70ef01583 100644
--- a/exercises/13_class/main.cpp
+++ b/exercises/13_class/main.cpp
@@ -15,10 +15,11 @@ class Fibonacci {
 public:
     // TODO: 实现构造器
     // Fibonacci()
+    Fibonacci() : cache{0, 1}, cached(2) {}
 
     // TODO: 实现正确的缓存优化斐波那契计算
     size_t get(int i) {
-        for (; false; ++cached) {
+        for (; cached <= i; ++cached) {
             cache[cached] = cache[cached - 1] + cache[cached - 2];
         }
         return cache[i];
diff --git a/exercises/14_class_destruct/main.cpp b/exercises/14_class_destruct/main.cpp
index 42150e8ca..df43950ac 100644
--- a/exercises/14_class_destruct/main.cpp
+++ b/exercises/14_class_destruct/main.cpp
@@ -11,14 +11,16 @@ class DynFibonacci {
 
 public:
     // TODO: 实现动态设置容量的构造器
-    DynFibonacci(int capacity): cache(new ?), cached(?) {}
+    DynFibonacci(int capacity): cache(new size_t[capacity]{0, 1}), cached(2) {}
 
     // TODO: 实现析构器，释放缓存空间
-    ~DynFibonacci();
+    ~DynFibonacci() {
+      delete []cache;
+    }
 
     // TODO: 实现正确的缓存优化斐波那契计算
     size_t get(int i) {
-        for (; false; ++cached) {
+        for (; cached <= i; ++cached) {
             cache[cached] = cache[cached - 1] + cache[cached - 2];
         }
         return cache[i];
diff --git a/exercises/15_class_clone/main.cpp b/exercises/15_class_clone/main.cpp
index f74b70391..35fbc6579 100644
--- a/exercises/15_class_clone/main.cpp
+++ b/exercises/15_class_clone/main.cpp
@@ -1,4 +1,5 @@
 #include "../exercise.h"
+#include <cstddef>
 
 // READ: 复制构造函数 <https://zh.cppreference.com/w/cpp/language/copy_constructor>
 // READ: 函数定义（显式弃置）<https://zh.cppreference.com/w/cpp/language/function>
@@ -7,20 +8,29 @@
 class DynFibonacci {
     size_t *cache;
     int cached;
-
+    int capacity;
 public:
     // TODO: 实现动态设置容量的构造器
-    DynFibonacci(int capacity): cache(new ?), cached(?) {}
+    DynFibonacci(int capacity): cache(new size_t[capacity]{0, 1}), cached(2), capacity(capacity) {}
 
     // TODO: 实现复制构造器
-    DynFibonacci(DynFibonacci const &) = delete;
+    DynFibonacci(DynFibonacci const &t) {
+      cached = t.cached;
+      capacity = t.capacity;
+      cache = new size_t[capacity];
+      for (int i = 0; i < cached; i ++) {
+        cache[i] = t.cache[i];
+      }
+    }
 
     // TODO: 实现析构器，释放缓存空间
-    ~DynFibonacci();
+    ~DynFibonacci() {
+      delete []cache;
+    }
 
     // TODO: 实现正确的缓存优化斐波那契计算
     size_t get(int i) {
-        for (; false; ++cached) {
+        for (; cached <= i; ++cached) {
             cache[cached] = cache[cached - 1] + cache[cached - 2];
         }
         return cache[i];
diff --git a/exercises/16_class_move/main.cpp b/exercises/16_class_move/main.cpp
index 8d2c421da..74333bba0 100644
--- a/exercises/16_class_move/main.cpp
+++ b/exercises/16_class_move/main.cpp
@@ -12,24 +12,46 @@
 class DynFibonacci {
     size_t *cache;
     int cached;
-
+    int capacity;
 public:
     // TODO: 实现动态设置容量的构造器
-    DynFibonacci(int capacity): cache(new ?), cached(?) {}
+    DynFibonacci(int capacity): cache(new size_t[capacity]{0, 1}), cached(2), capacity(capacity) {}
 
     // TODO: 实现移动构造器
-    DynFibonacci(DynFibonacci &&) noexcept = delete;
+    DynFibonacci(DynFibonacci &&t) noexcept {
+      cache = t.cache;
+      cached = t.cached;
+      capacity = t.capacity;
+      t.cache = nullptr;
+      t.cached = 0;
+      t.capacity = 0;
+    }
 
     // TODO: 实现移动赋值
     // NOTICE: ⚠ 注意移动到自身问题 ⚠
-    DynFibonacci &operator=(DynFibonacci &&) noexcept = delete;
+    DynFibonacci &operator=(DynFibonacci &&t) noexcept {
+      if (this == &t) {
+        return *this;
+      }
+      delete []cache;
+      cache = t.cache;
+      cached = t.cached;
+      capacity = t.capacity;
+      t.cache = nullptr;
+      t.cached = 0;
+      t.capacity = 0;
+      
+      return *this;
+    }
 
     // TODO: 实现析构器，释放缓存空间
-    ~DynFibonacci();
+    ~DynFibonacci() {
+      delete []cache;
+    }
 
     // TODO: 实现正确的缓存优化斐波那契计算
     size_t operator[](int i) {
-        for (; false; ++cached) {
+        for (; cached <= i; ++cached) {
             cache[cached] = cache[cached - 1] + cache[cached - 2];
         }
         return cache[i];
diff --git a/exercises/17_class_derive/main.cpp b/exercises/17_class_derive/main.cpp
index 819ae72fc..0c245df4f 100644
--- a/exercises/17_class_derive/main.cpp
+++ b/exercises/17_class_derive/main.cpp
@@ -50,9 +50,9 @@ int main(int argc, char **argv) {
     B b = B(3);
 
     // TODO: 补全三个类型的大小
-    static_assert(sizeof(X) == ?, "There is an int in X");
-    static_assert(sizeof(A) == ?, "There is an int in A");
-    static_assert(sizeof(B) == ?, "B is an A with an X");
+    static_assert(sizeof(X) == 4, "There is an int in X");
+    static_assert(sizeof(A) == 4, "There is an int in A");
+    static_assert(sizeof(B) == 8, "B is an A with an X");
 
     i = 0;
     std::cout << std::endl
diff --git a/exercises/18_class_virtual/main.cpp b/exercises/18_class_virtual/main.cpp
index ac6382413..344709e4c 100644
--- a/exercises/18_class_virtual/main.cpp
+++ b/exercises/18_class_virtual/main.cpp
@@ -42,38 +42,38 @@ int main(int argc, char **argv) {
     C c;
     D d;
 
-    ASSERT(a.virtual_name() == '?', MSG);
-    ASSERT(b.virtual_name() == '?', MSG);
-    ASSERT(c.virtual_name() == '?', MSG);
-    ASSERT(d.virtual_name() == '?', MSG);
-    ASSERT(a.direct_name() == '?', MSG);
-    ASSERT(b.direct_name() == '?', MSG);
-    ASSERT(c.direct_name() == '?', MSG);
-    ASSERT(d.direct_name() == '?', MSG);
+    ASSERT(a.virtual_name() == 'A', MSG);
+    ASSERT(b.virtual_name() == 'B', MSG);
+    ASSERT(c.virtual_name() == 'C', MSG);
+    ASSERT(d.virtual_name() == 'C', MSG);
+    ASSERT(a.direct_name() == 'A', MSG);
+    ASSERT(b.direct_name() == 'B', MSG);
+    ASSERT(c.direct_name() == 'C', MSG);
+    ASSERT(d.direct_name() == 'D', MSG);
 
     A &rab = b;
     B &rbc = c;
     C &rcd = d;
 
-    ASSERT(rab.virtual_name() == '?', MSG);
-    ASSERT(rbc.virtual_name() == '?', MSG);
-    ASSERT(rcd.virtual_name() == '?', MSG);
-    ASSERT(rab.direct_name() == '?', MSG);
-    ASSERT(rbc.direct_name() == '?', MSG);
-    ASSERT(rcd.direct_name() == '?', MSG);
+    ASSERT(rab.virtual_name() == 'B', MSG);
+    ASSERT(rbc.virtual_name() == 'C', MSG);
+    ASSERT(rcd.virtual_name() == 'C', MSG);
+    ASSERT(rab.direct_name() == 'A', MSG);
+    ASSERT(rbc.direct_name() == 'B', MSG);
+    ASSERT(rcd.direct_name() == 'C', MSG);
 
     A &rac = c;
     B &rbd = d;
 
-    ASSERT(rac.virtual_name() == '?', MSG);
-    ASSERT(rbd.virtual_name() == '?', MSG);
-    ASSERT(rac.direct_name() == '?', MSG);
-    ASSERT(rbd.direct_name() == '?', MSG);
+    ASSERT(rac.virtual_name() == 'C', MSG);
+    ASSERT(rbd.virtual_name() == 'C', MSG);
+    ASSERT(rac.direct_name() == 'A', MSG);
+    ASSERT(rbd.direct_name() == 'B', MSG);
 
     A &rad = d;
 
-    ASSERT(rad.virtual_name() == '?', MSG);
-    ASSERT(rad.direct_name() == '?', MSG);
+    ASSERT(rad.virtual_name() == 'C', MSG);
+    ASSERT(rad.direct_name() == 'A', MSG);
 
     return 0;
 }
diff --git a/exercises/19_class_virtual_destruct/main.cpp b/exercises/19_class_virtual_destruct/main.cpp
index cdd54f74f..50d85515b 100644
--- a/exercises/19_class_virtual_destruct/main.cpp
+++ b/exercises/19_class_virtual_destruct/main.cpp
@@ -5,12 +5,12 @@
 
 struct A {
     // TODO: 正确初始化静态字段
-    static int num_a = 0;
+    static int num_a;
 
     A() {
         ++num_a;
     }
-    ~A() {
+    virtual ~A() {
         --num_a;
     }
 
@@ -18,9 +18,10 @@ struct A {
         return 'A';
     }
 };
+int A::num_a = 0;
 struct B final : public A {
     // TODO: 正确初始化静态字段
-    static int num_b = 0;
+    static int num_b;
 
     B() {
         ++num_b;
@@ -33,14 +34,15 @@ struct B final : public A {
         return 'B';
     }
 };
+int B::num_b = 0;
 
 int main(int argc, char **argv) {
     auto a = new A;
     auto b = new B;
-    ASSERT(A::num_a == ?, "Fill in the correct value for A::num_a");
-    ASSERT(B::num_b == ?, "Fill in the correct value for B::num_b");
-    ASSERT(a->name() == '?', "Fill in the correct value for a->name()");
-    ASSERT(b->name() == '?', "Fill in the correct value for b->name()");
+    ASSERT(A::num_a == 2, "Fill in the correct value for A::num_a");
+    ASSERT(B::num_b == 1, "Fill in the correct value for B::num_b");
+    ASSERT(a->name() == 'A', "Fill in the correct value for a->name()");
+    ASSERT(b->name() == 'B', "Fill in the correct value for b->name()");
 
     delete a;
     delete b;
@@ -48,13 +50,13 @@ int main(int argc, char **argv) {
     ASSERT(B::num_b == 0, "Every B was destroyed");
 
     A *ab = new B;// 派生类指针可以随意转换为基类指针
-    ASSERT(A::num_a == ?, "Fill in the correct value for A::num_a");
-    ASSERT(B::num_b == ?, "Fill in the correct value for B::num_b");
-    ASSERT(ab->name() == '?', "Fill in the correct value for ab->name()");
+    ASSERT(A::num_a == 1, "Fill in the correct value for A::num_a");
+    ASSERT(B::num_b == 1, "Fill in the correct value for B::num_b");
+    ASSERT(ab->name() == 'B', "Fill in the correct value for ab->name()");
 
     // TODO: 基类指针无法随意转换为派生类指针，补全正确的转换语句
-    B &bb = *ab;
-    ASSERT(bb.name() == '?', "Fill in the correct value for bb->name()");
+    B &bb = dynamic_cast<B &>(*ab);
+    ASSERT(bb.name() == 'B', "Fill in the correct value for bb->name()");
 
     // TODO: ---- 以下代码不要修改，通过改正类定义解决编译问题 ----
     delete ab;// 通过指针可以删除指向的对象，即使是多态对象
diff --git a/exercises/20_function_template/main.cpp b/exercises/20_function_template/main.cpp
index cb6d978d3..2225bb989 100644
--- a/exercises/20_function_template/main.cpp
+++ b/exercises/20_function_template/main.cpp
@@ -2,7 +2,9 @@
 
 // READ: 函数模板 <https://zh.cppreference.com/w/cpp/language/function_template>
 // TODO: 将这个函数模板化
-int plus(int a, int b) {
+
+template<class T>
+T plus(T a, T b) {
     return a + b;
 }
 
@@ -11,10 +13,12 @@ int main(int argc, char **argv) {
     ASSERT(plus(1u, 2u) == 3u, "Plus two unsigned int");
 
     // THINK: 浮点数何时可以判断 ==？何时必须判断差值？
+    // - 如果小数可以被float精确表示时候，可以用==
+    // - 而如果是不可以被表示的小鼠则需要用差值
     ASSERT(plus(1.25f, 2.5f) == 3.75f, "Plus two float");
     ASSERT(plus(1.25, 2.5) == 3.75, "Plus two double");
     // TODO: 修改判断条件使测试通过
-    ASSERT(plus(0.1, 0.2) == 0.3, "How to make this pass?");
+    ASSERT(std::abs(plus(0.1, 0.2) - 0.3) < 1e-8, "How to make this pass?");
 
     return 0;
 }
diff --git a/exercises/21_runtime_datatype/main.cpp b/exercises/21_runtime_datatype/main.cpp
index 9c4bf376a..d1cc7b8f9 100644
--- a/exercises/21_runtime_datatype/main.cpp
+++ b/exercises/21_runtime_datatype/main.cpp
@@ -18,13 +18,19 @@ struct TaggedUnion {
 };
 
 // TODO: 将这个函数模板化用于 sigmoid_dyn
-float sigmoid(float x) {
+template<class T>
+T sigmoid(T x) {
     return 1 / (1 + std::exp(-x));
 }
 
 TaggedUnion sigmoid_dyn(TaggedUnion x) {
     TaggedUnion ans{x.type};
     // TODO: 根据 type 调用 sigmoid
+    if (x.type == DataType::Float) {
+      ans.f = sigmoid(x.f);
+    } else {
+      ans.d = sigmoid(x.d);
+    }
     return ans;
 }
 
diff --git a/exercises/22_class_template/main.cpp b/exercises/22_class_template/main.cpp
index d4985d904..00a7dcb5f 100644
--- a/exercises/22_class_template/main.cpp
+++ b/exercises/22_class_template/main.cpp
@@ -1,5 +1,7 @@
 #include "../exercise.h"
 #include <cstring>
+#include <functional>
+#include <numeric>
 // READ: 类模板 <https://zh.cppreference.com/w/cpp/language/class_template>
 
 template<class T>
@@ -8,7 +10,8 @@ struct Tensor4D {
     T *data;
 
     Tensor4D(unsigned int const shape_[4], T const *data_) {
-        unsigned int size = 1;
+        std::memcpy(shape, shape_, 4 * sizeof(unsigned int));
+        unsigned int size = std::accumulate(shape_, shape_ + 4, 1, std::multiplies<>());
         // TODO: 填入正确的 shape 并计算 size
         data = new T[size];
         std::memcpy(data, data_, size * sizeof(T));
@@ -28,6 +31,24 @@ struct Tensor4D {
     // 则 `this` 与 `others` 相加时，3 个形状为 `[1, 2, 1, 4]` 的子张量各自与 `others` 对应项相加。
     Tensor4D &operator+=(Tensor4D const &others) {
         // TODO: 实现单向广播的加法
+        for (unsigned int i = 0; i < shape[0]; ++i) {
+            for (unsigned int j = 0; j < shape[1]; ++j) {
+                for (unsigned int k = 0; k < shape[2]; ++k) {
+                    for (unsigned int l = 0; l < shape[3]; ++l) {
+                        unsigned int idx = (((i * shape[1]) + j) * shape[2] + k) * shape[3] + l;
+
+                        unsigned int oi = (others.shape[0] == 1) ? 0 : i;
+                        unsigned int oj = (others.shape[1] == 1) ? 0 : j;
+                        unsigned int ok = (others.shape[2] == 1) ? 0 : k;
+                        unsigned int ol = (others.shape[3] == 1) ? 0 : l;
+
+                        unsigned int oidx = (((oi * others.shape[1]) + oj) * others.shape[2] + ok) * others.shape[3] + ol;
+
+                        data[idx] += others.data[oidx];
+                    }
+                }
+            }
+        }
         return *this;
     }
 };
diff --git a/exercises/23_template_const/main.cpp b/exercises/23_template_const/main.cpp
index e0105e168..4ac243486 100644
--- a/exercises/23_template_const/main.cpp
+++ b/exercises/23_template_const/main.cpp
@@ -1,6 +1,7 @@
 #include "../exercise.h"
 #include <cstring>
-
+#include <functional>
+#include <numeric>
 // READ: 模板非类型实参 <https://zh.cppreference.com/w/cpp/language/template_parameters#%E6%A8%A1%E6%9D%BF%E9%9D%9E%E7%B1%BB%E5%9E%8B%E5%AE%9E%E5%8F%82>
 
 template<unsigned int N, class T>
@@ -9,7 +10,8 @@ struct Tensor {
     T *data;
 
     Tensor(unsigned int const shape_[N]) {
-        unsigned int size = 1;
+        std::memcpy(shape, shape_, N * sizeof(unsigned int));
+        unsigned int size = std::accumulate(shape_, shape_ + N, 1, std::multiplies<>());
         // TODO: 填入正确的 shape 并计算 size
         data = new T[size];
         std::memset(data, 0, size * sizeof(T));
@@ -34,7 +36,7 @@ struct Tensor {
         unsigned int index = 0;
         for (unsigned int i = 0; i < N; ++i) {
             ASSERT(indices[i] < shape[i], "Invalid index");
-            // TODO: 计算 index
+            index = index * shape[i] + indices[i];
         }
         return index;
     }
diff --git a/exercises/24_std_array/main.cpp b/exercises/24_std_array/main.cpp
index c29718d9d..1130c998f 100644
--- a/exercises/24_std_array/main.cpp
+++ b/exercises/24_std_array/main.cpp
@@ -8,21 +8,21 @@
 int main(int argc, char **argv) {
     {
         std::array<int, 5> arr{{1, 2, 3, 4, 5}};
-        ASSERT(arr.size() == ?, "Fill in the correct value.");
-        ASSERT(sizeof(arr) == ?, "Fill in the correct value.");
+        ASSERT(arr.size() == 5, "Fill in the correct value.");
+        ASSERT(sizeof(arr) == 20, "Fill in the correct value.");
         int ans[]{1, 2, 3, 4, 5};
-        ASSERT(std::memcmp(arr.?, ans, ?) == 0, "Fill in the correct values.");
+        ASSERT(std::memcmp(arr.data(), ans, sizeof(ans)) == 0, "Fill in the correct values.");
     }
     {
         std::array<double, 8> arr;
-        ASSERT(arr.size() == ?, "Fill in the correct value.");
-        ASSERT(sizeof(arr) == ?, "Fill in the correct value.");
+        ASSERT(arr.size() == 8, "Fill in the correct value.");
+        ASSERT(sizeof(arr) == 64, "Fill in the correct value.");
     }
     {
         std::array<char, 21> arr{"Hello, InfiniTensor!"};
-        ASSERT(arr.size() == ?, "Fill in the correct value.");
-        ASSERT(sizeof(arr) == ?, "Fill in the correct value.");
-        ASSERT(std::strcmp(arr.?, "Hello, InfiniTensor!") == 0, "Fill in the correct value.");
+        ASSERT(arr.size() == 21, "Fill in the correct value.");
+        ASSERT(sizeof(arr) == 21, "Fill in the correct value.");
+        ASSERT(std::strcmp(arr.data(), "Hello, InfiniTensor!") == 0, "Fill in the correct value.");
     }
     return 0;
 }
diff --git a/exercises/25_std_vector/main.cpp b/exercises/25_std_vector/main.cpp
index f9e41bb78..dba9df7fd 100644
--- a/exercises/25_std_vector/main.cpp
+++ b/exercises/25_std_vector/main.cpp
@@ -8,81 +8,85 @@
 int main(int argc, char **argv) {
     {
         std::vector<int> vec{1, 2, 3, 4, 5};
-        ASSERT(vec.size() == ?, "Fill in the correct value.");
+        ASSERT(vec.size() == 5, "Fill in the correct value.");
         // THINK: `std::vector` 的大小是什么意思？与什么有关？
-        ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+        // ANSWER: 等于vector对象中三个指针的大小
+        ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
         int ans[]{1, 2, 3, 4, 5};
-        ASSERT(std::memcmp(vec.?, ans, sizeof(ans)) == 0, "Fill in the correct values.");
+        ASSERT(std::memcmp(vec.data(), ans, sizeof(ans)) == 0, "Fill in the correct values.");
     }
     {
         std::vector<double> vec{1, 2, 3, 4, 5};
         {
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+            ASSERT(vec.size() == 5, "Fill in the correct value.");
+            ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
             double ans[]{1, 2, 3, 4, 5};
-            ASSERT(std::memcmp(vec.?, ans, sizeof(ans)) == 0, "Fill in the correct values.");
+            ASSERT(std::memcmp(vec.data(), ans, sizeof(ans)) == 0, "Fill in the correct values.");
         }
         {
             vec.push_back(6);
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+            // 1 2 3 4 5 6
+            ASSERT(vec.size() == 6, "Fill in the correct value.");
+            ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
             vec.pop_back();
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+            // 1 2 3 4 5
+            ASSERT(vec.size() == 5, "Fill in the correct value.");
+            ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
         }
         {
             vec[4] = 6;
-            ASSERT(vec[0] == ?, "Fill in the correct value.");
-            ASSERT(vec[1] == ?, "Fill in the correct value.");
-            ASSERT(vec[2] == ?, "Fill in the correct value.");
-            ASSERT(vec[3] == ?, "Fill in the correct value.");
-            ASSERT(vec[4] == ?, "Fill in the correct value.");
+            // 1 2 3 4 6
+            ASSERT(vec[0] == 1, "Fill in the correct value.");
+            ASSERT(vec[1] == 2, "Fill in the correct value.");
+            ASSERT(vec[2] == 3, "Fill in the correct value.");
+            ASSERT(vec[3] == 4, "Fill in the correct value.");
+            ASSERT(vec[4] == 6, "Fill in the correct value.");
         }
         {
             // THINK: `std::vector` 插入删除的时间复杂度是什么？
-            vec.insert(?, 1.5);
+            vec.insert(vec.begin() + 1, 1.5);
             ASSERT((vec == std::vector<double>{1, 1.5, 2, 3, 4, 6}), "Make this assertion pass.");
-            vec.erase(?);
+            vec.erase(vec.begin() + 3);
             ASSERT((vec == std::vector<double>{1, 1.5, 2, 4, 6}), "Make this assertion pass.");
         }
         {
             vec.shrink_to_fit();
-            ASSERT(vec.capacity() == ?, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 5, "Fill in the correct value.");
             vec.clear();
             ASSERT(vec.empty(), "`vec` is empty now.");
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(vec.capacity() == ?, "Fill in the correct value.");
+            ASSERT(vec.size() == 0, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 5, "Fill in the correct value.");
         }
     }
     {
-        std::vector<char> vec(?, ?); // TODO: 调用正确的构造函数
+        std::vector<char> vec(48, 'z'); // TODO: 调用正确的构造函数
         ASSERT(vec[0] == 'z', "Make this assertion pass.");
         ASSERT(vec[47] == 'z', "Make this assertion pass.");
         ASSERT(vec.size() == 48, "Make this assertion pass.");
-        ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+        ASSERT(sizeof(vec) == 24, "Fill in the correct value.");
         {
             auto capacity = vec.capacity();
             vec.resize(16);
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(vec.capacity() == ?, "Fill in a correct identifier.");
+            ASSERT(vec.size() == 16, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 48, "Fill in a correct identifier.");
         }
         {
             vec.reserve(256);
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(vec.capacity() == ?, "Fill in the correct value.");
+            ASSERT(vec.size() == 16, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 256, "Fill in the correct value.");
         }
         {
             vec.push_back('a');
             vec.push_back('b');
             vec.push_back('c');
             vec.push_back('d');
-            ASSERT(vec.size() == ?, "Fill in the correct value.");
-            ASSERT(vec.capacity() == ?, "Fill in the correct value.");
-            ASSERT(vec[15] == ?, "Fill in the correct value.");
-            ASSERT(vec[?] == 'a', "Fill in the correct value.");
-            ASSERT(vec[?] == 'b', "Fill in the correct value.");
-            ASSERT(vec[?] == 'c', "Fill in the correct value.");
-            ASSERT(vec[?] == 'd', "Fill in the correct value.");
+            ASSERT(vec.size() == 20, "Fill in the correct value.");
+            ASSERT(vec.capacity() == 256, "Fill in the correct value.");
+            ASSERT(vec[15] == 'z', "Fill in the correct value.");
+            ASSERT(vec[16] == 'a', "Fill in the correct value.");
+            ASSERT(vec[17] == 'b', "Fill in the correct value.");
+            ASSERT(vec[18] == 'c', "Fill in the correct value.");
+            ASSERT(vec[19] == 'd', "Fill in the correct value.");
         }
     }
 
diff --git a/exercises/26_std_vector_bool/main.cpp b/exercises/26_std_vector_bool/main.cpp
index b4ab4f9c4..15103c20e 100644
--- a/exercises/26_std_vector_bool/main.cpp
+++ b/exercises/26_std_vector_bool/main.cpp
@@ -6,29 +6,29 @@
 
 // TODO: 将下列 `?` 替换为正确的代码
 int main(int argc, char **argv) {
-    std::vector<bool> vec(?, ?);// TODO: 正确调用构造函数
+    std::vector<bool> vec(100, true);// TODO: 正确调用构造函数
     ASSERT(vec[0], "Make this assertion pass.");
     ASSERT(vec[99], "Make this assertion pass.");
     ASSERT(vec.size() == 100, "Make this assertion pass.");
     // NOTICE: 平台相关！注意 CI:Ubuntu 上的值。
     std::cout << "sizeof(std::vector<bool>) = " << sizeof(std::vector<bool>) << std::endl;
-    ASSERT(sizeof(vec) == ?, "Fill in the correct value.");
+    ASSERT(sizeof(vec) == 40, "Fill in the correct value.");
     {
         vec[20] = false;
-        ASSERT(?vec[20], "Fill in `vec[20]` or `!vec[20]`.");
+        ASSERT(!vec[20], "Fill in `vec[20]` or `!vec[20]`.");
     }
     {
         vec.push_back(false);
-        ASSERT(vec.size() == ?, "Fill in the correct value.");
-        ASSERT(?vec[100], "Fill in `vec[100]` or `!vec[100]`.");
+        ASSERT(vec.size() == 101, "Fill in the correct value.");
+        ASSERT(!vec[100], "Fill in `vec[100]` or `!vec[100]`.");
     }
     {
         auto ref = vec[30];
-        ASSERT(?ref, "Fill in `ref` or `!ref`");
+        ASSERT(ref, "Fill in `ref` or `!ref`");
         ref = false;
-        ASSERT(?ref, "Fill in `ref` or `!ref`");
+        ASSERT(!ref, "Fill in `ref` or `!ref`");
         // THINK: WHAT and WHY?
-        ASSERT(?vec[30], "Fill in `vec[30]` or `!vec[30]`.");
+        ASSERT(!vec[30], "Fill in `vec[30]` or `!vec[30]`.");
     }
     return 0;
 }
diff --git a/exercises/27_strides/main.cpp b/exercises/27_strides/main.cpp
index baceaf2a9..4f9e663b5 100644
--- a/exercises/27_strides/main.cpp
+++ b/exercises/27_strides/main.cpp
@@ -18,6 +18,12 @@ std::vector<udim> strides(std::vector<udim> const &shape) {
     // TODO: 完成函数体，根据张量形状计算张量连续存储时的步长。
     // READ: 逆向迭代器 std::vector::rbegin <https://zh.cppreference.com/w/cpp/container/vector/rbegin>
     //       使用逆向迭代器可能可以简化代码
+    int cnt = shape.size();
+    int cur = 1;
+    for (auto it = shape.rbegin(); it != shape.rend(); it ++) {
+      strides[-- cnt] = cur;
+      cur *= *it;
+    }
     return strides;
 }
 
diff --git a/exercises/28_std_string/main.cpp b/exercises/28_std_string/main.cpp
index d8b276274..63d21f11f 100644
--- a/exercises/28_std_string/main.cpp
+++ b/exercises/28_std_string/main.cpp
@@ -6,13 +6,13 @@
 int main(int argc, char **argv) {
     // READ: 字符串字面量 <https://zh.cppreference.com/w/cpp/string/basic_string/operator%22%22s>
     using namespace std::string_literals;
-    auto hello = "Hello"s;
+    auto hello = "Hello"s; 
     auto world = "world";
     // READ: `decltype` 表达式 <https://zh.cppreference.com/w/cpp/language/decltype>
     // READ: `std::is_same_v` 元编程判别 <https://zh.cppreference.com/w/cpp/types/is_same>
-    ASSERT((std::is_same_v<decltype(hello), ?>), "Fill in the missing type.");
-    ASSERT((std::is_same_v<decltype(world), ?>), "Fill in the missing type.");
+    ASSERT((std::is_same_v<decltype(hello), std::string>), "Fill in the missing type.");
+    ASSERT((std::is_same_v<decltype(world), const char *>), "Fill in the missing type.");
     // TODO: 将 `?` 替换为正确的字符串
-    ASSERT(hello + ", " + world + '!' == "?", "Fill in the missing string.");
+    ASSERT(hello + ", " + world + '!' == "Hello, world!", "Fill in the missing string.");
     return 0;
 }
diff --git a/exercises/29_std_map/main.cpp b/exercises/29_std_map/main.cpp
index fcccca347..e1b4c7b1e 100644
--- a/exercises/29_std_map/main.cpp
+++ b/exercises/29_std_map/main.cpp
@@ -7,11 +7,13 @@
 template<class k, class v>
 bool key_exists(std::map<k, v> const &map, k const &key) {
     // TODO: 实现函数
+    return map.count(key);
 }
 
 template<class k, class v>
 void set(std::map<k, v> &map, k key, v value) {
     // TODO: 实现函数
+    map[key] = value;
 }
 
 // ---- 不要修改以下代码 ----
diff --git a/exercises/30_std_unique_ptr/main.cpp b/exercises/30_std_unique_ptr/main.cpp
index 9b98b5794..7256c03e7 100644
--- a/exercises/30_std_unique_ptr/main.cpp
+++ b/exercises/30_std_unique_ptr/main.cpp
@@ -1,5 +1,6 @@
 #include "../exercise.h"
 #include <cstring>
+#include <iostream>
 #include <memory>
 #include <string>
 #include <vector>
@@ -49,12 +50,21 @@ int main(int argc, char **argv) {
 
     // ---- 不要修改以上代码 ----
 
+    // DEBUG: 打印实际结果
+    for (size_t i = 0; i < 3; ++i) {
+        std::cout << "problems[" << i << "] size=" << problems[i].size() << ": ";
+        for (size_t j = 0; j < problems[i].size(); ++j) {
+            std::cout << "\"" << problems[i][j] << "\" ";
+        }
+        std::cout << std::endl;
+    }
+
     std::vector<const char *> answers[]{
         {"fd"},
         // TODO: 分析 problems[1] 中资源的生命周期，将记录填入 `std::vector`
         // NOTICE: 此题结果依赖对象析构逻辑，平台相关，提交时以 CI 实际运行平台为准
-        {"", "", "", "", "", "", "", ""},
-        {"", "", "", "", "", "", "", ""},
+        {"d", "ffr"},
+        {"d", "d", "r"},
     };
 
     // ---- 不要修改以下代码 ----
diff --git a/exercises/31_std_shared_ptr/main.cpp b/exercises/31_std_shared_ptr/main.cpp
index febbbcc6f..6fcd8b880 100644
--- a/exercises/31_std_shared_ptr/main.cpp
+++ b/exercises/31_std_shared_ptr/main.cpp
@@ -10,36 +10,36 @@ int main(int argc, char **argv) {
     std::shared_ptr<int> ptrs[]{shared, shared, shared};
 
     std::weak_ptr<int> observer = shared;
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 4, "");
 
     ptrs[0].reset();
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 3, "");
 
     ptrs[1] = nullptr;
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 2, "");
 
     ptrs[2] = std::make_shared<int>(*shared);
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 1, "");
 
     ptrs[0] = shared;
     ptrs[1] = shared;
     ptrs[2] = std::move(shared);
-    ASSERT(observer.use_count() == ?, "");
-
-    std::ignore = std::move(ptrs[0]);
+    ASSERT(observer.use_count() == 3, "");
+ 
+    std::ignore = std::move(ptrs[0]); // move走了但没存 usecount = 2
     ptrs[1] = std::move(ptrs[1]);
     ptrs[1] = std::move(ptrs[2]);
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 2, ""); // usecount = 1
 
     shared = observer.lock();
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 3, ""); // lock 会增加usecount usecount = 2
 
     shared = nullptr;
     for (auto &ptr : ptrs) ptr = nullptr;
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 0, "");
 
     shared = observer.lock();
-    ASSERT(observer.use_count() == ?, "");
+    ASSERT(observer.use_count() == 0, "");
 
     return 0;
 }
diff --git a/exercises/32_std_transform/main.cpp b/exercises/32_std_transform/main.cpp
index f4dc25a5c..52a520749 100644
--- a/exercises/32_std_transform/main.cpp
+++ b/exercises/32_std_transform/main.cpp
@@ -1,5 +1,6 @@
 #include "../exercise.h"
 #include <algorithm>
+#include <functional>
 #include <string>
 #include <vector>
 
@@ -9,6 +10,11 @@
 int main(int argc, char **argv) {
     std::vector<int> val{8, 13, 21, 34, 55};
     // TODO: 调用 `std::transform`，将 `v` 中的每个元素乘以 2，并转换为字符串，存入 `ans`
+    std::vector<std::string> ans;
+    ans.resize(val.size());
+    std::transform(val.begin(), val.end(), ans.begin(), [&](int x){
+      return std::to_string(x * 2);
+    });
     // std::vector<std::string> ans
     ASSERT(ans.size() == val.size(), "ans size should be equal to val size");
     ASSERT(ans[0] == "16", "ans[0] should be 16");
diff --git a/exercises/33_std_accumulate/main.cpp b/exercises/33_std_accumulate/main.cpp
index 6326929d5..25e8e3a77 100644
--- a/exercises/33_std_accumulate/main.cpp
+++ b/exercises/33_std_accumulate/main.cpp
@@ -1,4 +1,5 @@
 #include "../exercise.h"
+#include <functional>
 #include <numeric>
 
 // READ: `std::accumulate` <https://zh.cppreference.com/w/cpp/algorithm/accumulate>
@@ -6,12 +7,13 @@
 int main(int argc, char **argv) {
     using DataType = float;
     int shape[]{1, 3, 224, 224};
+    int len = sizeof(shape) / sizeof(int);
     // TODO: 调用 `std::accumulate` 计算：
     //       - 数据类型为 float；
     //       - 形状为 shape；
     //       - 连续存储；
     //       的张量占用的字节数
-    // int size =
+    int size = 4 * std::accumulate(shape, shape + len, 1, std::multiplies<>());
     ASSERT(size == 602112, "4x1x3x224x224 = 602112");
     return 0;
 }