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Author: ivanmmarkovic

Ch03. Basic Data Structures/Stack/stack-array/Stack.py

@@ -0,0 +1,46 @@
+class Stack:
+    def __init__(self):
+        self.stack = []
+
+    def isEmpty(self):
+        return len(self.stack) == 0
+
+    def size(self):
+        return len(self.stack)
+
+    def peek(self):
+        return self.stack[len(self.stack) - 1]
+
+    def pop(self):
+        # not checking if stack is empty
+        # https://github.com/ivanmmarkovic/Problem-Solving-with-Algorithms-and-Data-Structures-using-Python/issues/1
+        return self.stack.pop()
+
+    def push(self, item):
+        self.stack.append(item)
+
+        
+'''
+this solution is slower
+previous
+############
+1. pop - pop() - O(1)
+2. push - append() - O(1)
+this
+############
+1. pop - pop(i) - O(k)
+2. push - insert(i) - O(n)
+class Stack:
+    def __init__(self):
+        self.stack: list = []
+    def isEmpty(self)->bool:
+        return len(self.stack) == 0
+    def size(self)->int:
+        return len(self.stack)
+    def push(self, item):
+        self.stack.insert(0, item)
+    def pop(self):
+        return self.stack.pop(0)
+    def peek(self):
+        return self.stack[0]
+'''