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ospluscode · web-flow · commit cbf8e7c4bb65 · 2021-03-12T20:45:40.000-08:00
Stack implementation using Linked List
diff --git a/stackLinkedList.py b/stackLinkedList.py
@@ -0,0 +1,65 @@
+# Stack implementation using LinkedList
+# Simply, the idea is to insert a node to the head of LinkedList
+# each time we push an element to the Stack
+# All Time and Space complexity O(1)
+
+class Node:
+    def __init__(self, value = None):
+        self.value = value
+        self.next = None
+
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+    
+    def __iter__(self):
+        current_node = self.head
+        while current_node:
+            yield current_node
+            current_node = current_node.next
+
+
+class Stack:
+    def __init__(self):
+        self.linked_list = LinkedList()
+    
+    def __str__(self):
+        values = [str(v.value) for v in self.linked_list]
+        return '\n'.join(values)
+
+
+    def isEmpty(self):
+        if self.linked_list.head == None:
+            return True
+        else:
+            return False
+
+
+    # add node to the head/first
+    def push(self, value):
+        node = Node(value)
+        node.next = self.linked_list.head
+        self.linked_list.head = node
+
+
+    def peek(self):
+        if self.isEmpty():
+            return "Stack is empty"
+        else:
+            node_value = self.linked_list.head.value
+            return node_value
+
+
+    # get the head/first node
+    def pop(self):
+        if self.isEmpty():
+            return "Stack is empty"
+        else:
+            node_value = self.linked_list.head.value
+            self.linked_list.head = self.linked_list.head.next
+            return node_value
+
+
+    def delete(self):
+        self.linked_list.head = None
