How to implement stack in C programming ?

In continuation of demonstrating simple implementation of data structures, as we shown in our last post “How to implement linked list in C programming ?”, in this post we will show how you can implement simple stack in C programming language. Stack is nothing but a one this kept on another, where we define how many maximum elements can be kept in one stack and what is the current size of the stack.

$ vim simple_stack.c

#include <stdio.h>
#include <stdlib.h>

struct stack {
        int top;
        int max_elements_in_stack;
        int *array;
};

void push(struct stack *s, int value) {
        s->top = ++s->top;
        s->array[s->top] = value;
}

int pop(struct stack *s) {
        int val = s->array[s->top];
        s->top = --s->top;
        return val;
}

struct stack *init_stack(int count) {
        struct stack *s = (struct stack *)malloc(sizeof(struct stack));
        s->top = -1;
        s->max_elements_in_stack = count;
        s->array = (int *) malloc(sizeof(int) * count);
}

int main(int argc, char **argv) {
        int max_elements_in_stack = 100;
        struct stack *st = init_stack(max_elements_in_stack);

        push(st, 10);
        push(st, 20);
        push(st, 30);
        push(st, 40);
        printf("popped value is %d\n", pop(st));
        printf("popped value is %d\n", pop(st));
        return 0;
}

The above program, implements simple stack which holds maximum 100 elements and we initialise this stack with “init_stack” and simple function “push” adds an element into stack and pop removes an element from stack [ here stack is just a simple array of integers]

We can compile the program as,

$ gcc -o simple_stack simple_stack.c

$ ./simple_stack 
popped value is 40
popped value is 30