Merge pull request #48 from narayancse/main

Stack Implementation in Python

Stack/Stack Implementation.py

@@ -0,0 +1,74 @@
+# Custom stack implementation in Python
+class Stack:
+
+    # Constructor to initialize the stack
+    def __init__(self, size):
+        self.arr = [None] * size
+        self.capacity = size
+        self.top = -1
+
+    # Function to add an element `val` to the stack
+    def push(self, val):
+        if self.isFull():
+            print('Stack Overflow!! Calling exit()…')
+            exit(-1)
+
+        print(f'Inserting {val} into the stack…')
+        self.top = self.top + 1
+        self.arr[self.top] = val
+
+    # Function to pop a top element from the stack
+    def pop(self):
+        # check for stack underflow
+        if self.isEmpty():
+            print('Stack Underflow!! Calling exit()…')
+            exit(-1)
+
+        print(f'Removing {self.peek()} from the stack')
+
+        # decrease stack size by 1 and (optionally) return the popped element
+        top = self.arr[self.top]
+        self.top = self.top - 1
+        return top
+
+    # Function to return the top element of the stack
+    def peek(self):
+        if self.isEmpty():
+            exit(-1)
+        return self.arr[self.top]
+
+    # Function to return the size of the stack
+    def size(self):
+        return self.top + 1
+
+    # Function to check if the stack is empty or not
+    def isEmpty(self):
+        return self.size() == 0
+
+    # Function to check if the stack is full or not
+    def isFull(self):
+        return self.size() == self.capacity
+
+
+if __name__ == '__main__':
+
+    stack = Stack(3)
+
+    stack.push(1)       # Inserting 1 in the stack
+    stack.push(2)       # Inserting 2 in the stack
+
+    stack.pop()         # removing the top element (2)
+    stack.pop()         # removing the top element (1)
+
+    stack.push(3)       # Inserting 3 in the stack
+
+    print('Top element is', stack.peek())
+    print('The stack size is', stack.size())
+
+    stack.pop()         # removing the top element (3)
+
+    # check if the stack is empty
+    if stack.isEmpty():
+        print('The stack is empty')
+    else:
+        print('The stack is not empty')