Hackathon update

data_structure_algorithms.py

@@ -0,0 +1,80 @@
+### 1. Reverse a String Using a Stack
+def reverse_string(s: str) -> str:
+    stack = []
+
+    for char in s:
+        stack.append(char)
+
+    reversed_string = ""
+    while stack:
+        reversed_string += stack.pop()
+
+    return reversed_string
+
+input_string = "hackathon"
+output_string = reverse_string(input_string)
+print(output_string)  
+
+
+### 2. Implement a Queue Using Two Stacks
+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()
+
+q = QueueWithStacks()
+q.enqueue(10)
+q.enqueue(20)
+q.enqueue(30)
+print(q.dequeue())  
+print(q.dequeue())  
+print(q.dequeue())  
+
+### 3. Find the Maximum Element in a List Using a Linked List
+class ListNode:
+    def __init__(self, data: int):
+        self.data = data
+        self.next = None
+
+class MyLinkedList:
+    def __init__(self):
+        self.head = None
+
+    def append(self, data: int):
+        new_node = ListNode(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) -> int:
+        if not self.head:
+            raise ValueError("The linked list is empty")
+
+        max_value = self.head.data
+        current = self.head
+        while current:
+            if current.data > max_value:
+                max_value = current.data
+            current = current.next
+        return max_value
+
+
+ll = MyLinkedList()
+ll.append(7)
+ll.append(2)
+ll.append(9)
+ll.append(5)
+print(ll.find_max())