Stack in Python

Author: Deepali-Srivastava

stack-and-queue/stack-array-1.py

@@ -0,0 +1,82 @@
+# Copyright (C) Deepali Srivastava - All Rights Reserved
+# This code is part of DSA course available on CourseGalaxy.com  
+
+class StackEmptyError(Exception):
+    pass
+
+class StackFullError(Exception):
+    pass
+
+class Stack:
+    
+    def __init__(self,max_size=10):
+        self.items = [None] * max_size
+        self.count = 0 
+
+    def size(self):
+        return self.count 
+
+    def is_empty(self):
+        return self.count == 0
+
+    def is_full(self):
+        return self.count == len(self.items)
+    
+    def push(self,x):
+        if self.is_full():
+            raise StackFullError("Stack is full, can't push")
+
+        self.items[self.count] = x
+        self.count+=1
+            
+    def pop(self):
+        if self.is_empty():
+            raise StackEmptyError("Stack is empty, can't pop")
+             
+        x = self.items[self.count-1]
+        self.items[self.count-1] = None
+        self.count-=1
+        return x          
+
+    def peek(self):
+        if self.is_empty():
+            raise StackEmptyError("Stack is empty, can't peek")
+
+        return self.items[self.count-1] 
+    
+    def display(self):
+        print(self.items)
+     
+#########################################################
+
+if __name__ == "__main__":
+
+    st = Stack(8)
+    
+    while True:
+        print("1.Push") 
+        print("2.Pop") 
+        print("3.Peek") 
+        print("4.Size")
+        print("4.Display") 
+        print("6.Quit") 
+         
+        choice = int(input("Enter your choice : "))
+
+        if choice == 1:
+            x=int(input("Enter the element to be pushed : "))
+            st.push(x) 
+        elif choice == 2:
+            x=st.pop() 
+            print("Popped element is : " , x) 
+        elif choice == 3:
+            print("Element at the top is : " , st.peek()) 
+        elif choice == 4:
+            print("Size of stack " , st.size()) 
+        elif choice == 5:
+            st.display() 
+        elif choice == 6:
+          break
+        else:
+          print("Wrong choice") 
+        print()

stack-and-queue/stack-array.py

@@ -0,0 +1,66 @@
+# Copyright (C) Deepali Srivastava - All Rights Reserved
+# This code is part of DSA course available on CourseGalaxy.com  
+
+class EmptyStackError(Exception):
+    pass
+
+class Stack:
+        
+    def __init__(self):
+        self.items = []
+
+    def is_empty(self):
+        return self.items == []
+
+    def size(self):
+        return len(self.items)
+
+    def push(self, item):
+        self.items.append(item)
+
+    def pop(self):
+        if self.is_empty():
+            raise EmptyStackError("Stack is empty")
+        return self.items.pop()
+    
+    def peek(self):
+        if self.is_empty():
+            raise EmptyStackError("Stack is empty")
+        return self.items[len(self.items)-1]
+
+    def display(self):
+        print(self.items)
+
+###########################################################
+
+if __name__ == "__main__":
+    st = Stack()
+
+    while True:
+        print("1.Push") 
+        print("2.Pop") 
+        print("3.Peek") 
+        print("4.Size")
+        print("5.Display") 
+        print("6.Quit")
+         
+        choice = int(input("Enter your choice : "))
+
+        if choice == 1:
+            x=int(input("Enter the element to be pushed : "))
+            st.push(x) 
+        elif choice == 2:
+            x=st.pop() 
+            print("Popped element is : " , x) 
+        elif choice == 3:
+            print("Element at the top is : " , st.peek()) 
+        elif choice == 4:
+            print("Size of stack " , st.size()) 
+        elif choice == 5:
+            st.display()         
+        elif choice == 6:
+          break;
+        else:
+          print("Wrong choice") 
+        print() 
+

stack-and-queue/stack-linked.py

@@ -0,0 +1,94 @@
+# Copyright (C) Deepali Srivastava - All Rights Reserved
+# This code is part of DSA course available on CourseGalaxy.com  
+
+class EmptyStackError(Exception):
+    pass
+
+class Node:
+
+    def __init__(self,value):
+        self.info = value 
+        self.link = None
+      
+class Stack:
+
+    def __init__(self):
+        self.top = None
+       
+    def is_empty(self):
+        return self.top == None
+   
+    def size(self):
+
+        if self.is_empty():
+            retun 0
+
+        count=0
+        p = self.top 
+        while p is not None:
+            count+=1
+            p = p.link 
+        return count
+
+    def push(self, data):
+        temp = Node(data)
+        temp.link = self.top
+        self.top = temp
+       
+    def peek(self):
+        if self.is_empty():
+            raise EmptyStackError("Stack is empty")
+        return self.top.info
+    
+    def pop(self):      
+        if self.is_empty():
+            raise EmptyStackError("Stack is empty")
+        popped = self.top.info
+        self.top = self.top.link
+        return popped
+
+   def display(self):
+        if self.is_empty():
+            print("Stack is empty")
+            return
+        
+        print("Stack is :   ")
+        p = self.top 
+        while p is not None:
+            print(p.info , " ")
+            p = p.link 
+           
+#########################################################################################
+            
+if __name__ == "__main__":
+    st = Stack()
+
+    while True:
+        print("1.Push") 
+        print("2.Pop") 
+        print("3.Peek") 
+        print("5.Size") 
+        print("4.Display")  
+        print("6.Quit") 
+         
+        choice = int(input("Enter your choice : "))
+
+        if choice == 1:
+            x=int(input("Enter the element to be pushed : "))
+            st.push(x) 
+        elif choice == 2:
+            x=st.pop() 
+            print("Popped element is : " , x) 
+        elif choice == 3:
+            print("Element at the top is : " , st.peek()) 
+        elif choice == 4:
+            print("Size of stack " , st.size())
+        elif choice == 5:
+            st.display()  
+        elif choice == 6:
+          break;
+        else:
+          print("Wrong choice") 
+        print()
+     
+