C program for array implementation of stack




#include <stdio.h>

#include <stdlib.h>

#include <limits.h>

 

// A structure to represent a stack

struct Stack

{

    int top;

    unsigned capacity;

    int* array;

};

 

// function to create a stack of given capacity. It initializes size of

// stack as 0

struct Stack* createStack(unsigned capacity)

{

    struct Stack* stack = (struct Stack*) malloc(sizeof(struct Stack));

    stack->capacity = capacity;

    stack->top = -1;

    stack->array = (int*) malloc(stack->capacity * sizeof(int));

    return stack;

}

 

// Stack is full when top is equal to the last index

int isFull(struct Stack* stack)

{   return stack->top == stack->capacity - 1; }

 

// Stack is empty when top is equal to -1

int isEmpty(struct Stack* stack)

{   return stack->top == -1;  }

 

// Function to add an item to stack.  It increases top by 1

void push(struct Stack* stack, int item)

{

    if (isFull(stack))

        return;

    stack->array[++stack->top] = item;

    printf("%d pushed to stack\n", item);

}

 

// Function to remove an item from stack.  It decreases top by 1

int pop(struct Stack* stack)

{

    if (isEmpty(stack))

        return INT_MIN;

    return stack->array[stack->top--];

}

// Driver program to test above functions

int main()

{

    struct Stack* stack = createStack(100);

 

    push(stack, 10);

    push(stack, 20);

    push(stack, 30);

 

    printf("%d popped from stack\n", pop(stack));

 

    return 0;

}

OUTPUT:

10 pushed to stack
20 pushed to stack
30 pushed to stack
30 popped from stack
Top item is 20