写了很久了，没有注意到的问题挺多的

首先，算平均分时，人数为0可能会被0除要特判

然后排名当时自以为写了一个很对的方法结果不对

最后一次交的时候没有删文件输入输出疯狂TLE我也是醉了。。。。

好在最后成功解决hhh

#include<bits/stdc++.h>
using namespace std;

struct node
{
    string SID,nam;
    int CID;
    int yw,yy,sx,bc,sum;
}a[1000];

const double eps = 1e-5;
int tot;

void mainSPMS()   //打印主菜单
{
    printf("Welcome to Student Performance Management System (SPMS).\n\n");
    printf("1 - Add\n2 - Remove\n3 - Query\n");
    printf("4 - Show ranking\n5 - Show Statistics\n0 - Exit\n\n");
}

void add()   //添加学生信息
{
    while(1)
    {
        printf("Please enter the SID, CID, name and four scores. Enter 0 to finish.\n");
        cin >> a[++tot].SID;
        if(a[tot].SID == "0")
        {
            tot--;
            return;
        }
        cin >> a[tot].CID >> a[tot].nam;
        cin >> a[tot].yw >> a[tot].sx >> a[tot].yy >> a[tot].bc;
        for(int i = 1;i < tot; ++i)
            if(a[i].SID == a[tot].SID)
            {
                printf("Duplicated SID.\n");
                tot--;
                continue;
            }
        a[tot].sum = a[tot].yw + a[tot].sx + a[tot].yy + a[tot].bc;
    }
}

void Remove()   //删除学生信息
{
    while(1)
    {
        printf("Please enter SID or name. Enter 0 to finish.\n");
        string s;
        int sum = 0;
        cin >> s;
        if(s == "0") return;
        for(int i = 1;i <= tot; ++i)
        {
            if(a[i].SID == s || a[i].nam == s)
            {
                a[i].SID  = a[i].nam = "";
                a[i].CID = a[i].yw = a[i].sx = a[i].yy = a[i].bc = a[i].sum = 0;
                sum++;
            }
        }
        printf("%d student(s) removed.\n",sum);
    }
}

int ran(int x)
{
    int ans = 1;
    for(int i = 1;i <= tot; ++i)
        if(a[i].sum > x) ans++;
    return ans;
}

void query()
{
    while(1)
    {
        printf("Please enter SID or name. Enter 0 to finish.\n");
        string s;
        int sum = 0;
        cin >> s;
        if(s == "0") return;
        for(int i = 1;i <= tot; ++i)
        {
            if(s == a[i].SID || s == a[i].nam)
            {
                cout << ran(a[i].sum) << ' ' << a[i].SID << ' ' << a[i].CID << ' ' << a[i].nam << ' ';
                cout << a[i].yw << ' ' << a[i].sx << ' ' << a[i].yy << ' ' << a[i].bc << ' ';
                double tt = a[i].sum * 1.0 / 4 + eps;
                printf("%d %.2f\n",a[i].sum ,tt);
            }
        }
    }
}

void showr()
{
    printf("Showing the ranklist hurts students' self-esteem. Don't do that.\n");
}

void shows()
{
    printf("Please enter class ID, 0 for the whole statistics.\n");
    int s;
    cin >> s;
    int yw2 = 0,sx2 = 0,yy2 = 0,bc2 = 0,ki[5] = {0},num = 0,sumyw = 0,sumsx = 0,sumyy = 0,sumbc = 0;
    for(int i = 1;i <= tot; ++i)
    {
        if(a[i].CID == s || s == 0)
        {
            if(a[i].SID == "") continue;
            int k = 0;
            if(a[i].yw < 60) yw2++,k++;
            sumyw += a[i].yw;
            if(a[i].sx < 60) sx2++,k++;
            sumsx += a[i].sx;
            if(a[i].yy < 60) yy2++,k++;
            sumyy += a[i].yy;
            if(a[i].bc < 60) bc2++,k++;
            sumbc += a[i].bc;
            ki[k]++; num++;
        }
    }
    printf("Chinese\nAverage Score: %.2f\n",num ? sumyw * 1.0 / num + eps:0.00);
    printf("Number of passed students: %d\nNumber of failed students: %d\n\n",num - yw2,yw2);
    printf("Mathematics\nAverage Score: %.2f\n",num ? sumsx * 1.0 / num + eps:0.00);
    printf("Number of passed students: %d\nNumber of failed students: %d\n\n",num - sx2,sx2);
    printf("English\nAverage Score: %.2f\n",num ? sumyy * 1.0 / num + eps:0.00);
    printf("Number of passed students: %d\nNumber of failed students: %d\n\n",num - yy2,yy2);
    printf("Programming\nAverage Score: %.2f\n",num ? sumbc * 1.0 / num + eps:0.00);
    printf("Number of passed students: %d\nNumber of failed students: %d\n\n",num - bc2,bc2);

    printf("Overall:\nNumber of students who passed all subjects: %d\n",ki[0]);
    printf("Number of students who passed 3 or more subjects: %d\n",ki[0] + ki[1]);
    printf("Number of students who passed 2 or more subjects: %d\n",ki[0] + ki[1] + ki[2]);
    printf("Number of students who passed 1 or more subjects: %d\n",num - ki[4]);
    printf("Number of students who failed all subjects: %d\n\n",ki[4]);
}

int main()
{
    tot = 0;
    //freopen("1.in","r",stdin);
    //freopen("1.out","w",stdout);
    while(1)
    {
        mainSPMS();  //打印主菜单
        int x;
        scanf("%d",&x);
        if(x == 0) return 0;   // 0 Exit 退出
        if(x == 1) add();
        if(x == 2) Remove();
        if(x == 3) query();
        if(x == 4) showr();
        if(x == 5) shows();
    }
    return 0;
}