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Author: ivanmmarkovic

Ch03. Basic Data Structures/Stack/stack-linked-list/node.py

@@ -0,0 +1,5 @@
+
+class Node:
+    def __init__(self, key = None, next = None):
+        self.key = key
+        self.next = next

Ch03. Basic Data Structures/Stack/stack-linked-list/stack.py

@@ -0,0 +1,47 @@
+from node import Node
+
+class Stack:
+    def __init__(self):
+        self.head: Node = None
+        self.length: int = 0
+
+    def isEmpty(self):
+        return self.head is None
+        # self.length == 0
+
+    def size(self):
+        # avoid linked list traversal
+        return self.length
+
+    def peek(self):
+        if self.isEmpty():
+            raise Exception('Stack is empty')
+        else:
+            return self.head.key
+
+    def pop(self):
+        if self.isEmpty():
+            raise Exception('Stack is empty')
+        else:
+            retNode: Node = self.head
+            self.head = self.head.next
+            self.length -= 1
+            return retNode.key
+
+    def push(self, item):
+        self.length += 1
+        self.head = Node(item, self.head)
+
+
+s = Stack()
+print(s.isEmpty())
+s.push(4)
+s.push('dog')
+print(s.peek())
+s.push(True)
+print(s.size())
+print(s.isEmpty())
+s.push(8.4)
+print(s.pop())
+print(s.pop())
+print(s.size())