/* 
* Code example for CP264 Data Structures II
* array stack
* HBF 
*/
#include <stdio.h>
#define MAX 10

void push(int stack[], int *top, int val);
void pop(int stack[], int *top);
int  peek(int stack[], int top);
void display_stack(int stack[], int top);

int main() {
  int stack[MAX];
  int top = -1;
  
  printf("push:\n");
  push(stack, &top, 1);
  push(stack, &top, 2);
  push(stack, &top, 3);
  printf("display:\n");
  display_stack(stack, top);
  printf("\npeek:%d\n", peek(stack, top));
  printf("pop\n");
  pop(stack, &top);
  printf("display:\n");
  display_stack(stack, top);
  
  return 0;
}

void push(int stack[], int *top, int val) {
  if (*top == MAX-1) {
    printf("\n STACK OVERFLOW");
  } else {
    *top = *top + 1;
    stack[*top] = val;
  }
}

void pop(int stack[], int *top) {
  if (*top == -1) {
    printf("\n STACK UNDERFLOW");
  } else {
    *top = *top - 1;
  }
}

int peek(int stack[], int top) {
  if (top == -1) {
    printf("\n STACK IS EMPTY");
    return -1;
  } else
    return (stack[top]);
}

void display_stack(int stack[], int top) {
  int i;
  if (top == -1)
    printf("\nSTACK IS EMPTY");
  else {
    for (i = top; i >= 0; i--) {
      printf("%d ", stack[i]);
    }
  }
}

/*
push:
display:
3 2 1
peek:3
pop
display:
2 1
*/