From 6cbc1a5d43661d8f1f5e20586e3d46dd26de836e Mon Sep 17 00:00:00 2001
From: NyancheraMakaye <emakaye.nyanchera.com>
Date: Sat, 31 Aug 2024 23:51:18 +0300
Subject: [PATCH]  Implemented a stack data structure to reverse a
 string,implemented a queue using two stacks,Implemented a sinly linked list
 and found the maximum element in the list.

---
 task1.py | 39 +++++++++++++++++++++++++++++++++++++++
 task2.py | 30 ++++++++++++++++++++++++++++++
 task3.py | 45 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 114 insertions(+)
 create mode 100644 task1.py
 create mode 100644 task2.py
 create mode 100644 task3.py

diff --git a/task1.py b/task1.py
new file mode 100644
index 0000000..8c753d1
--- /dev/null
+++ b/task1.py
@@ -0,0 +1,39 @@
+class Stack:
+    def __init__(self):
+        self.items = []
+
+    def push(self, item):
+        self.items.append(item)
+
+    def pop(self):
+        if not self.is_empty():
+            return self.items.pop()
+        else:
+            return None
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+def reverse_string(s: str) -> str:
+    """
+    Reverses a string using a stack data structure.
+
+    Args:
+        s (str): The input string to be reversed.
+
+    Returns:
+        str: The reversed string.
+    """
+    stack = Stack()
+    for char in s:
+        stack.push(char)
+
+    reversed_s = ""
+    while not stack.is_empty():
+        reversed_s += stack.pop()
+
+    return reversed_s
+
+# Example usage:
+input_str = "Hello, World!"
+print(reverse_string(input_str))  # Output: "!dlroW ,olleH"
\ No newline at end of file
diff --git a/task2.py b/task2.py
new file mode 100644
index 0000000..64e9e88
--- /dev/null
+++ b/task2.py
@@ -0,0 +1,30 @@
+class QueueWithStacks:
+    def __init__(self):
+        # Initialize two empty stacks
+        self.stack1 = []
+        self.stack2 = []
+
+    def enqueue(self, x: int):
+        # Add an element to the queue by pushing it onto stack1
+        self.stack1.append(x)
+
+    def dequeue(self) -> int:
+        # If both stacks are empty, the queue is empty
+        if not self.stack1 and not self.stack2:
+            raise IndexError("Cannot dequeue from an empty queue")
+
+        # If stack2 is empty, pop all elements from stack1 and push them onto stack2
+        if not self.stack2:
+            while self.stack1:
+                self.stack2.append(self.stack1.pop())
+
+        # The front element of the queue is now at the top of stack2
+        return self.stack2.pop()
+    
+queue = QueueWithStacks()
+queue.enqueue(1)
+queue.enqueue(2)
+queue.enqueue(3)
+print(queue.dequeue())  
+print(queue.dequeue())  
+print(queue.dequeue())  
\ No newline at end of file
diff --git a/task3.py b/task3.py
new file mode 100644
index 0000000..aff59bf
--- /dev/null
+++ b/task3.py
@@ -0,0 +1,45 @@
+class Node:
+    def __init__(self, data):
+        self.data = data
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+
+    def append(self, data):
+        new_node = Node(data)
+        if not self.head:
+            self.head = new_node
+            return
+        current = self.head
+        while current.next:
+            current = current.next
+        current.next = new_node
+
+    def find_max(self):
+        """
+        Finds the maximum element in the linked list.
+
+        Returns:
+            int: The maximum element in the list.
+        """
+        if not self.head:
+            return None
+        max_element = self.head.data
+        current = self.head.next
+        while current:
+            if current.data > max_element:
+                max_element = current.data
+            current = current.next
+        return max_element
+
+# Example usage:
+linked_list = LinkedList()
+linked_list.append(50)
+linked_list.append(10)
+linked_list.append(37)
+linked_list.append(20)
+linked_list.append(15)
+
+print(linked_list.find_max())  
\ No newline at end of file