这是我的老代码：

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll N=110;
struct oier{
	ll y,m,d,num;
	string name;
}; 
bool cmp(oier x,oier z){
	return x.y<z.y || (x.y==z.y && (x.m<z.m || (x.m==z.m && (x.d<z.d || (x.d==z.d && x.num<z.num))))); 
}
oier a[N];
int main(){
	ll n;
	cin>>n;
	ll s;
	for(s=1;s<=n;s++){
		cin>>a[s].name>>a[s].y>>a[s].m>>a[s].d;
	}
	sort(a+1,a+n+1,cmp);
	for(s=1;s<=n;s++){
		cout<<a[s].name<<endl;
	}
    return 0;
}

这是我自己修改过的：

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll N=110;
struct oier{
	ll y,m,d,num;
	string name;
}; 
bool cmp(oier x,oier z){
	return x.y<z.y || (x.y==z.y && (x.m<z.m || (x.m==z.m && (x.d<z.d || (x.d==z.d && x.num<z.num))))); 
}
oier a[N];
int main(){
	ll n;
	cin>>n;
	ll s;
	for(s=1;s<=n;s++){
		cin>>a[s].name>>a[s].y>>a[s].m>>a[s].d;
		a[s].num=s;//此处
	}
	sort(a+1,a+n+1,cmp);
	for(s=1;s<=n;s++){
		cout<<a[s].name<<endl;
	}
    return 0;
}

然鹅，我发现老代码可以AC#5，修改过的却不行！ 求助QwQ，玄关！