Adding Solutions.py

Solutions.py

@@ -0,0 +1,94 @@
+# Task 1: Reverse a string using a stack
+def reverse_string(s: str) -> str:
+    # Creating an empty list
+    stack = []
+    # Pushing each character of string to stack
+    for char in s:
+        stack.append(char)
+    # Pop each character from stack and form a reversed string
+    reversed_string = ''
+    while stack:
+        reversed_string += stack.pop()
+    return reversed_string
+
+print(reverse_string('hello'))
+
+# Task 2: Implement a queue using two stacks.
+class QueueWithStack:
+    def __init__(self):
+        self.stack1 = []
+        self.stack2 = []
+
+    def enqueue(self, x: int):
+        # pushing new elements to stack 1
+        self.stack1.append(x)
+
+    def dequeue(self) -> int:
+        # if stack2 is empty, what's on stack1 must be moved to stack2
+        if not self.stack2:
+            while self.stack1:
+                self.stack2.append(self.stack1.pop())
+        # an error that must be returned when trying to dequeue an empty queue
+        if not self.stack2:
+            raise IndexError("dequeue from an empty queue")            
+
+        return self.stack2.pop()
+
+# test example:
+q = QueueWithStack()  
+q.enqueue(1)
+q.enqueue(2) 
+print(q.dequeue())
+print(q.dequeue())
+
+
+# Task 3: Find the Maximum Element in a List Using a Linked List
+class Node:
+    def __init__(self, data: int):
+        self.data = data 
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+
+    def append(self, data: int):
+        # Create a new node with the given data
+        new_node = Node(data)
+
+        # If the list is empty, make the new node the head
+        if self.head is None:
+            self.head = new_node
+        else:
+            # loop through the list to find the last node and append the new node
+            current = self.head
+            while current.next:
+                current = current.next
+            current.next = new_node
+
+    # Creating a function that will go through the list and return the maximum value
+    def find_max(self) -> int:
+        # If the list is empty, raise an error
+        if self.head is None:
+            raise ValueError("List is empty")
+
+        # Initialize max_value with the data of the head node
+        max_value = self.head.data
+        current = self.head
+
+        # loop through the list and update max_value if a larger element is found
+        while current is not None:
+            if current.data > max_value:
+                max_value = current.data
+            current = current.next
+
+        return max_value
+
+# Test Example:
+ll = LinkedList()
+ll.append(3)
+ll.append(1)
+ll.append(4)
+ll.append(2)
+print(ll.find_max())
+