题解（数组版）

#include<bits/stdc++.h>
using namespace std;
int p[10005],TOP=0;
void push(int i){
	p[++TOP]=i;
}
void pop(){
	TOP--;
}
bool empty(){
	return TOP==0;
}
int top(){
	return p[TOP];
}
int size(){
	return TOP;
}
int main(){
    int n,a;
    string b;
    scanf("%d",&n);
    while(n--){
    	cin>>b;
    	if(b=="push"){
    		cin>>a;
    		push(a);
		}else if(b=="pop"){
			if(empty()){
				printf("pop fail\n");
				continue;
			}else {
				printf("pop %d\n",top());
				pop();
			}
		}else if(b=="top"){
			if(empty()){
				printf("top fail\n");
			}else printf("top = %d\n",top());
		}else if(b=="size"){
			printf("size = %d\n",size());
		}else if(b=="empty"){
			if(empty()){
				cout<<"yes"<<endl;
			}else{
				cout<<"no"<<endl;
			}
		}
	}
    return 0;
}