栈的操作

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

#define ERROR 0
#define OK 1

typedef struct Stack {
    int *elements;
    int max_size, top_index;
}Stack;

void init(Stack *s, int length_input) {
    s->elements = (int *)malloc(sizeof(int) * length_input);
    s->max_size = length_input;
    s->top_index = -1;
}

int push(Stack *s, int element) {
    if (s->top_index >= s->max_size - 1) {
        return ERROR;
    }
    s->top_index++;
    s->elements[s->top_index] = element;
    return OK;
}

int pop(Stack *s) {
    if (s->top_index < 0) {
        return ERROR;
    }
    s->top_index--;
    return OK;
}

// 请在下面实现输出栈顶函数 top
int top(Stack *s){
    return s->elements[s->top_index];
}


void clear(Stack *s) {
    free(s->elements);
    free(s);
}

int main() {
    int n, m;
    scanf("%d %d", &n, &m);
    Stack *stack = (Stack *)malloc(sizeof(Stack));
    init(stack, n);
    for (int i = 1; i <= m; i++) {
        int opr;
        scanf("%d", &opr);
        if (opr == 0) {
            int element;
            scanf("%d", &element);
            if (push(stack, element)) {
                printf("push success!\n");
            } else {
                printf("push failed!\n");
            }
        } else if (opr == 1) {
            if (pop(stack)) {
                printf("pop success!\n");
            } else {
                printf("pop failed!\n");
            }
        }
        else if(opr == 2){
            printf("%d\n",top(stack));
        }
    }
    clear(stack);
    return 0;
}