7-47 打印选课学生名单 (25分)--桶排

先将所有学生的信息按姓名字典序排序，再根据每个学生选的课程号码分别放入相应链表存储，最后输出每个链表的信息。

/*每个课程当做一个桶，桶里面用链表按学生姓名字典序存储学生，最后直接输出每个桶的内容，排序的时候使用头插法*/
#include<iostream>
#include <map>
#include <cstring>
#include <algorithm>
using namespace std;
struct Stu
{
    char name[5];
    int course[20];
    int num;
};
bool cmp(Stu s1, Stu s2)//后面要使用头插法建链表，所以先按字典序逆序排序
{
    if (strcmp(s1.name, s2.name) > 0)
    {
        return true;
    }
    else return false;
}
    struct course
    {
        char s_name[5];
        struct course* next;
    };
int main()
{
    int N, K;
    cin >> N >> K;
    long long int* course_num = new long long int[K + 1]{ 0 };
    struct Stu* stu = new struct Stu[N];
    struct course* crs = new struct course[K + 1];
    for (int i = 1; i <= K; i++)
    {
        crs[i].next = NULL;
    }
    for (int i = 0; i < N; i++)
    {
    scanf("%s",stu[i].name);
    scanf("%d",&stu[i].num);
        for (int j = 0; j < stu[i].num; j++)
        {
      scanf("%d",&stu[i].course[j]);
            course_num[stu[i].course[j]]++;
        }
    }
    sort(stu, stu + N, cmp);
    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < stu[i].num; j++)
        {
            int c = stu[i].course[j];        
            struct course* s = new course;
            strcpy(s->s_name, stu[i].name);
            s->next = NULL;
            if (NULL == crs[c].next)
            {
                crs[c].next = s;
            }
            else
            {
                struct course* p = crs[c].next;
                s->next = p;
                crs[c].next = s;
            }
        }
    }
    for (int i = 1; i <= K; i++)
    {
        struct course* p = NULL;
        p = crs[i].next;
    printf("%d %lld
",i,course_num[i]);
        while (NULL != p)
        {
      printf("%s
",p->s_name);
            p = p->next;
        }
    }
    return 0;
}