Answers

Question 1.py

@@ -0,0 +1,50 @@
+# Question 1
+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()
+        raise IndexError("pop from an empty stack")
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+    def peek(self):
+        if not self.is_empty():
+            return self.items[-1]
+        raise IndexError("peek from an empty stack")
+
+def reverse_string(s: str) -> str:
+    stack = Stack()
+
+    # Push all characters of the string onto the stack
+    for char in s:
+        stack.push(char)
+
+    # Pop all characters from the stack and build the reversed string
+    reversed_str = ''
+    while not stack.is_empty():
+        reversed_str += stack.pop()
+
+    return reversed_str
+
+def main():
+    # Prompt user for input
+    user_input = input("Enter a string to reverse: ")
+
+    # Reverse the string
+    reversed_string = reverse_string(user_input)
+
+    # Output the reversed string
+    print(f"Reversed string: {reversed_string}")
+
+# Run the main function if this script is executed
+if __name__ == "__main__":
+    main()
+
+

Question 2.py

@@ -0,0 +1,25 @@
+# Question 2
+class QueueWithStacks:
+    def __init__(self):
+        self.stack1 = []  # Stack used for enqueue operations
+        self.stack2 = []  # Stack used for dequeue operations
+
+    def enqueue(self, x: int):
+        # Push the element onto stack1
+        self.stack1.append(x)
+
+    def dequeue(self) -> int:
+        # If stack2 is empty, transfer elements from stack1 to stack2
+        if not self.stack2:
+            while self.stack1:
+                self.stack2.append(self.stack1.pop())
+
+        # If stack2 is still empty, the queue is empty and we cannot dequeue
+        if not self.stack2:
+            raise IndexError("dequeue from an empty queue")
+
+        # Pop the top element from stack2
+        return self.stack2.pop()
+
+
+

Question 3.py

@@ -0,0 +1,35 @@
+# Question 3
+class Node:
+    def __init__(self, value: int):
+        self.value = value
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+
+    def append(self, value: int):
+        """Append a new node with the given value to the end of the list."""
+        new_node = Node(value)
+        if not self.head:
+            self.head = new_node
+        else:
+            current = self.head
+            while current.next:
+                current = current.next
+            current.next = new_node
+
+    def find_max(self) -> int:
+        """Find the maximum value in the linked list."""
+        if not self.head:
+            raise ValueError("The linked list is empty")
+
+        current = self.head
+        max_value = current.value
+
+        while current:
+            if current.value > max_value:
+                max_value = current.value
+            current = current.next
+
+        return max_value