stack-array.c

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

#define MAX_SIZE 100

typedef struct Stack {
  int arr[MAX_SIZE];
  int top;
} Stack;

Stack* init();
void push(Stack *s, int data);
int pop(Stack *s);
int peak(Stack *s);

int main() {
  Stack *stack = init();

  push(stack, 1);
  push(stack, 2);
  push(stack, 5);
  push(stack, 3);

  printf("Peak %d\n", peak(stack));

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

  printf("Peak %d\n", peak(stack));

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

  return 0;
}

Stack* init() {
  Stack *s = (Stack*)malloc(sizeof(Stack));
  s->top = -1;
  return s;
}

void push(Stack *s, int data) {
  s->arr[++(s->top)] = data;
}

int pop(Stack *s) {
  if (s->top == -1) return -1;
  
  return s->arr[s->top--];
}

int peak(Stack *s) {
  if (s->top == -1) return -1;

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