1047. Student List for Course (25)

#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

#define K 2501

inline int id(char s[]) {
return ((s[0]-'A')*26*26 + (s[1]-'A')*26 + (s[2]-'A'))*10 + (s[3]-'0');
}

inline char * sid(int id) {
static char s[5];

s[3] = id%10 + '0';
id /= 10;
for(int i = 2; i >= 0; i --) {
s[i] = id % 26 + 'A';
id /= 26;
}
return s;
}

int main(int argc, char **argv) {
vector<int> course[K];
int n, k;
cin >> n >> k;
for(int i = 0; i < n; i ++) {
char stu[5];
int cc;
scanf("%s %d", stu, &cc);
int uid = id(stu);
for(int i = 0; i < cc; i ++) {
int c;
scanf("%d", &c);
course[c].push_back(uid);
}
}

for(int i = 1; i <= k; i ++) {
printf("%d %d\n", i, course[i].size());
sort(course[i].begin(), course[i].end());
for(int j = 0; j < course[i].size(); j ++)
printf("%s\n", sid(course[i][j]));
}

return 0;
}