Solutions

linked_list.py

@@ -0,0 +1,40 @@
+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+
+    def append(self, value):
+        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:
+        if not self.head:
+            return float('-inf')  # Return negative infinity if the list is empty
+
+        max_value = self.head.value
+        current = self.head
+        while current:
+            if current.value > max_value:
+                max_value = current.value
+            current = current.next
+
+        return max_value
+
+# Example usage
+if __name__ == "__main__":
+    ll = LinkedList()
+    ll.append(3)
+    ll.append(1)
+    ll.append(4)
+    ll.append(2)
+    print(ll.find_max())  # Output: 4

queue_with_stacks.py

@@ -0,0 +1,21 @@
+class QueueWithStacks:
+    def __init__(self):
+        self.stack1 = []
+        self.stack2 = []
+
+    def enqueue(self, x: int):
+        self.stack1.append(x)
+
+    def dequeue(self) -> int:
+        if not self.stack2:
+            while self.stack1:
+                self.stack2.append(self.stack1.pop())
+        return self.stack2.pop()
+
+# Example usage
+if __name__ == "__main__":
+    q = QueueWithStacks()
+    q.enqueue(1)
+    q.enqueue(2)
+    print(q.dequeue())  # Output: 1
+    print(q.dequeue())  # Output: 2

reverse_string.py

@@ -0,0 +1,28 @@
+class Stack:
+    def __init__(self):
+        self.items = []
+
+    def push(self, item):
+        self.items.append(item)
+
+    def pop(self):
+        return self.items.pop()
+
+    def is_empty(self):
+        return len(self.items) == 0
+
+def reverse_string(s: str) -> str:
+    stack = Stack()
+    for char in s:
+        stack.push(char)
+
+    reversed_str = ''
+    while not stack.is_empty():
+        reversed_str += stack.pop()
+
+    return reversed_str
+
+# Example usage
+if __name__ == "__main__":
+    input_str = "hello"
+    print(reverse_string(input_str))  # Output: "olleh"