《算法笔记》6.1小节——C++标准模板库(STL)介绍-＞vector的常见用法详解-＞问题 B: Student List for Course (25)-优快云博客

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给定浙江大学40000名学生的注册课程列表，程序需按课程编号顺序输出每个课程的学生名单。输入包含学生数量、课程数量以及每位学生的姓名、选课数和课程编号。代码使用C++实现，通过vector存储数据并排序输出。

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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

代码C++

// 
#include <iostream>
#include<cstdio>
#include<cstring>
#include<vector>
#include<algorithm>
#include<string>
using namespace std;
const int maxn = 2510;
vector<string> selectCourse[maxn];
int main() {
	int n, k;
	scanf("%d%d", &n, &k);
	string name;
	for (int i = 0; i < n; i++) {
		// 输入必须用cin，string读入和输出整个字符串，则只能用cin和cout:
		cin >> name;
		//scanf("%s", name);
		int course, x;
		scanf("%d", &x);
		for (int j = 0; j < x; j++) {
			scanf("%d", &course);
			selectCourse[course].push_back(name);
		}
	}
	for (int i = 1; i <= k; i++) {
		sort(selectCourse[i].begin(), selectCourse[i].end());
		printf("%d %d\n", i, selectCourse[i].size());
		//for (vector<string>::iterator it = selectCourse[i].begin(); it != selectCourse[i].end(); it++) {
		//	cout << *it << endl;
		//}
		for (int j = 0; j < selectCourse[i].size(); j++) {
			//printf("%s\n", selectCourse[i][j]);
			// 输出必须用cout，why,同上
			cout << selectCourse[i][j] << endl;
		}
	}
	return 0;
}