Student List for Course (25) cid=100000596

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本文介绍了一个课程注册系统的实现方法，该系统能够处理大量学生选课数据，并按课程编号输出选择每门课程的学生名单及其数量。

题目描述：

Zhejiang University has 40000 students and provides 2500 courses. Now given the registered course list of each student, you are supposed to output the student name lists of all the courses.

输入：

Each input file contains one test case. For each case, the first line contains 2 numbers: N (<=40000), the total number of students, and K (<=2500), the total number of courses. Then N lines follow, each contains a student's name (3 capital English letters plus a one-digit number), a positive number C (<=20) which is the number of courses that this student has registered, and then followed by C course numbers. For the sake of simplicity, the courses are numbered from 1 to K.

输出：

For each test case, print the student name lists of all the courses in increasing order of the course numbers. For each course, first print in one line the course number and the number of registered students, separated by a space. Then output the students' names in alphabetical order. Each name occupies a line.

样例输入：

10 5
ZOE1 2 4 5
ANN0 3 5 2 1
BOB5 5 3 4 2 1 5
JOE4 1 2
JAY9 4 1 2 5 4
FRA8 3 4 2 5
DON2 2 4 5
AMY7 1 5
KAT3 3 5 4 2
LOR6 4 2 4 1 5

样例输出：

1 4
ANN0
BOB5
JAY9
LOR6
2 7
ANN0
BOB5
FRA8
JAY9
JOE4
KAT3
LOR6
3 1
BOB5
4 7
BOB5
DON2
FRA8
JAY9
KAT3
LOR6
ZOE1
5 9
AMY7
ANN0
BOB5
DON2
FRA8
JAY9
KAT3
LOR6
ZOE1

思路：

使用一个vector<string> course_list[课程数量]来保存数据，其中第一维代表课程，第二维度存储选了这门课的学生姓名。

第一纬度下标-1就是课程号，例如保存选了1号课程学生姓名的vector可以用course_list[0]表示。在读取所有数据后，对每个第二维vector用sort进行排序然后输出。

我的解决方案：

#include <iostream>
#include <stdio.h>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    int n,k,c,cur_course;
    string name;
    scanf("%d %d",&n,&k);
    vector<string> course_list[k];
    //course_list下标-1是课程号
    for(int i=0;i<n;i++) {
        cin >> name;
        cin >> c;
        for (int i = 0; i < c; i++) {
            scanf("%d", &cur_course);
            course_list[cur_course - 1].push_back(name);
        }
    }
    for(int i=0;i<k;i++){
        sort(course_list[i].begin(),course_list[i].end());
    }
    for(int i=0;i<k;i++){
        cout<<i+1<<' '<<course_list[i].size()<<endl;
        for(int j=0;j<course_list[i].size();j++){
            cout<<course_list[i][j]<<endl;
        }
    }

return 0;
}