Stack

Concept

Stack is a data structure which operates on LIFO(last in first out) principle.The element that we push in last,pops out first.Here's an example

Top keeps track of the top element of the stack.

Lets see how we can implement a stack using an array.

Declaring the stack structure

typedef struct 
{
        int top,arr[15];
}stack;

Declare stack variable

stack s;

Initialize 

s.top = -1

Check empty stack

s.top == -1

Push 

top is incremented and new element is pushed in at that position.

void push()
{
    int element;
    do
    {
        if(s.top==(SIZE-1))
        {
            printf("Stack full");
            break;
        }

        printf("Enter element to be pushed ");
        scanf("%d",&element);

        s.arr[++s.top] = element;

        printf("Push more elements ? ");

        fflush(stdin);
    }while(getchar()=='y');
}   

Pop  

the top element is returned from the stack and top is decremented.

int pop()
{
    if(isEmpty())
    {
        printf("Stack is empty.Can't pop.");
        return -1;
    }

    return s.arr[s.top--];
}

Complete code

More

Stack using Queue

Stack using linked list