// stack using STL
#include<stack>
#include<iostream>
using namespace std;
int main(){
stack<int>s;
// push
s.push(2);
s.push(4);
s.push(5);
s.push(7);
// 2 4 5 7
//pop
s.pop(); // removed 7
//top
cout<<" top = "<<s.top(); // 5
// is empty
if(s.empty())cout<<"\nyes";
else cout<<"\nNO";
// size
cout<<" \nsize = "<<s.size(); // 3
}
// stack using array
// library
#include<stdio.h>
#include<stdlib.h>
// make structure maxsize , top , *items
struct stack{
int maxSize;
int top;
int *items;
};
// initialization
struct stack* newStack(int capacity){
struct stack *p = (struct stack *)malloc(sizeof(struct stack));
p->maxSize = capacity;
p->top = -1;
p->items = (int *)malloc(sizeof(int) * capacity);
return p;
}
// operations for our stack
// top
int top(struct stack* p ){
return p->items[p->top];
}
// isEmpty
int isEmpty(struct stack* p ){
return p->top == -1;
}
// isFull
int isFull(struct stack *p){
return p->top + 1 == p->maxSize;
}
// size
int size(struct stack * p){
return p->top + 1;
}
// push
void push(struct stack* p , int element){ // 12 3 4 4 3
if(isFull(p)){
printf("Overflow!\n");
}else{
p->items[++p->top] = element;
}
}
// pop
int pop(struct stack * p ){
if(isEmpty(p)){
printf("Underflow!");
}else{
return p->items[p->top--];
}
}
int main(){
struct stack * s = newStack(5);
push(s,1);
push(s,5);
push(s,3);
push(s,6);
// 1 5 3 6
printf("%d\n",top(s));
printf("%d",size(s));
return 0;
}
CREATING STACK USING PYTHON
OPERATIONS:
1- PUSH
2- POP
OTHER OPERATIONS:
1- IS EMPTY
2- SIZE
3- TOP
CODE :
We can implement stack using :
1- list
2- collections.deque
3- queue.LifoQueue
1 - IMPLEMENTING STACK USING LIST
CODE:
stack = [] // list is created to be used as stack
stack.append('a') // append() push the element in stack which is actually a list
stack.append('b')
stack.append('c')
print(stack.pop()) // pop() is used to pop / delete element on top of listprint(stack.pop())print(stack.pop())print(stack)
2- IMPLEMENTING STACK USING collections.deque
from collections import deque // importing the librarystack = deque() // initializing a variablestack.append('a') // append function to insert elementstack.append('b')stack.append('c')print(stack.pop()) // pop() function to remove the top elementprint(stack.pop())print(stack.pop())print(stack)
from queue import LifoQueue
stack = LifoQueue(maxsize = 5) // initializing stack with maxsize = 5
print(stack.qsize()) // show the number of elements in the stack
stack.put('a') // put() is used to push elements in the stack
stack.put('b')
stack.put('c')
print("Full: ", stack.full()) // is the stack full or does stack contain maxsize elements
print(stack.get()) // return and remove the top element of the stack
print(stack.get())
print(stack.get())
print("Is Empty : ", stack.empty()) // test is the stack empty or not
STACK IN STL
Standard library provides us stack container with number of built in features.
STACK TEMPLATE :
template <class T, class Container = deque<T> > class stack;#include <iostream>
#include <stack> // for using stack container
using namespace std;
int main()
{
int sum = 0;
stack<int> mystack; // declaring stack
mystack.push(21); // inserting element
mystack.push(32);
mystack.push(23);
mystack.push(63);
mystack.push(212);
while (!mystack.empty()) { // checking the empty condition
sum = sum + mystack.top(); // checking the top element
mystack.pop(); // performing pop operation
}
cout << sum;
return 0;
}
IMPLEMENTING STACK USING LINKEDLIST
This provide us ability to define our own data structure and point it to another same data structure using pointers which can be done dynamically .
Here , Since we are using Linked list we will use malloc and free ( in C ) to allocate memory and then deallocate it when needed.
Structure or Linked list Node
Header Files
OPERATIONS
NOTE : Since , performing operations on head is easy and efficient so we will choose head node as top node and will perform all operations on head node
1- PUSH
2- IS EMPTY
3- TOP
4- POP
