结构中的成绩排名与查找

#include<iostream>
#include<algorithm>
#include<stdlib.h> 
#include<string.h>
using namespace std;
struct stu {
    char name[20];
    char id[20];
    int grade;
    int rank;
}arr[100];
int main() {
    int n; int j = 0; char patter[20]; char temp[5];
    cin >> n; cin >> patter;
    for (int i = 0; i < n; i++) {  // 结构的输入
        cin >> arr[i].name; cin >> arr[i].id; cin >> temp; arr[i].grade =atoi(temp);
    }
    for (int i = 0; i < n; i++) {  // 结构的稳定降序排序——buble sort
        for (j = 1; j < n - i; j++) {
            if (arr[j - 1].grade < arr[j].grade) swap(arr[j - 1], arr[j]);
        }
    }
    int rank = 1; arr[1].rank = 1; int count = 1;// 真实排名
    for (j = 1; j < n; j++) { // 排名编号 相同排名一致，但仍按人数计算的排名，不是按编号递减的排名
        if (arr[j].grade != arr[j - 1].grade) { rank++; count++; arr[j].rank = count; }
        else {
            arr[j].rank = rank; count++;
        }
    }
    int num = atoi(patter);
    if(isalpha(patter[0])) { // 人名查找  
        for (j = 0; j < n; j++) {
            if (strstr(arr[j].name, patter) != NULL) {// 注意每一项之间是否打印了空格
                if (arr[j].grade == 0)  // 成绩的缺考项输出转化
                    cout << arr[j].name << " " << arr[j].id << " n/a n/a" << endl;
                else
                    cout << arr[j].name << " " << arr[j].id << " " << arr[j].grade << " " << arr[j].rank << endl;
            }
        }
    }
    else if ( num<= 100) { // 成绩查找
        for (j = 0; j < n; j++) {
            if (arr[j].grade == num) 
            {
                if (arr[j].grade == 0)
                    cout << arr[j].name << " " << arr[j].id << " n/a n/a" << endl;
                else
                    cout << arr[j].name << " " << arr[j].id << " " << arr[j].grade << " " << arr[j].rank << endl;
            }
        }
    }
    else {// id查找
        for (j = 0; j < n; j++) {
            if (strstr(arr[j].id, patter) != NULL)
            {
                if (arr[j].grade == 0)
                    cout << arr[j].name <<" " << arr[j].id << " n/a n/a" << endl;
                else
                    cout << arr[j].name <<" " << arr[j].id <<" " << arr[j].grade << " " << arr[j].rank << endl;
            }
        }
    }
    return 0;
}