考试成绩和学号的（结构体）排序

使学号和成绩关联，然后成绩sort，学号也跟着改变。
代码：#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>
using namespace std;
const int MaxN = 1e5;

struct node {
int val;
int id;
}arr[MaxN];

int cmp(node a, node b) {
if(a.val == b.val) return a.id < b.id;
return a.val < b.val;
}

int main()
{
int n;
scanf("%d", &n);
for(int i = 1; i <= n; i++) {
scanf("%d", &arr[i].val);
arr[i].id = i;
}
sort(arr + 1, arr + n + 1, cmp);
for(int i = 1; i <= n; i++)
printf("%d %d\n", arr[i].id, arr[i].val);
}