solution

• 测试点3超时：命令为3时，用unordered_map而非map，否则会超时

#include<iostream>
#include<string>
#include<algorithm>
#include<unordered_map>
using namespace std;
const int maxn = 1e4 + 10;
struct stu{
	string id;
	int score;
	friend bool operator < (stu &s1, stu &s2){
		if(s1.score == s2.score) return s1.id < s2.id;
		return s1.score > s2.score;
	}
}stus[maxn], temp[maxn];
int main(){
	int n, m, com, cnt, sum;
	string coms;
	cin >> n >> m;
	for(int i = 0; i < n; i++){
		cin >> stus[i].id >> stus[i].score;
	}
	for(int j = 1; j <= m; j++){
		cnt = sum = 0;
		cin >> com >> coms;
		cout << "Case " << j << ": " << com << " " << coms << endl;
		if(com == 1){
			for(int i = 0; i < n; i++){
				if(stus[i].id.substr(0, 1) == coms){
					temp[cnt].id = stus[i].id;
					temp[cnt++].score = stus[i].score; 
				}
			}
		}
		else if(com == 2){
			for(int i = 0; i < n; i++){
				if(stus[i].id.substr(1, 3) == coms){
					 cnt++;
					 sum += stus[i].score;
				}
			}
			if(cnt) cout << cnt << " " << sum << endl;
		}
		else{
			unordered_map<string, int> mp;
			for(int i = 0; i < n; i++){
				if(stus[i].id.substr(4, 6) == coms) mp[stus[i].id.substr(1, 3)]++; 
			}
			for(unordered_map<string, int>::iterator it = mp.begin(); it != mp.end(); it++){
				temp[cnt].id = it -> first;
				temp[cnt++].score = it -> second;
			}
		}
		if(com != 2){
			sort(temp, temp + cnt);
			for(int i = 0; i < cnt; i++){
				cout << temp[i].id << " " << temp[i].score << endl;
			}
		}
		if(!cnt) cout << "NA" << endl;
	}
	return 0;
} 

或者

#include<iostream>
#include<string>
#include<algorithm>
#include<unordered_map>
#include<vector>
using namespace std;
const int maxn = 1e4 + 10;
struct stu{
	string id;
	int score;
	friend bool operator < (stu &s1, stu &s2){
		if(s1.score == s2.score) return s1.id < s2.id;
		return s1.score > s2.score;
	}
}stus[maxn];
int main(){
	int n, m, com, cnt, sum;
	string coms;
	cin >> n >> m;
	for(int i = 0; i < n; i++){
		cin >> stus[i].id >> stus[i].score;
	}
	for(int j = 1; j <= m; j++){
		cnt = sum = 0;
		vector<stu> vs;
		cin >> com >> coms;
		cout << "Case " << j << ": " << com << " " << coms << endl;
		if(com == 1){
			for(int i = 0; i < n; i++){
				if(stus[i].id.substr(0, 1) == coms) vs.push_back(stus[i]);
			}
		}
		else if(com == 2){
			for(int i = 0; i < n; i++){
				if(stus[i].id.substr(1, 3) == coms){
					 cnt++;
					 sum += stus[i].score;
				}
			}
			if(cnt) cout << cnt << " " << sum << endl;
		}
		else{
			unordered_map<string, int> mp;
			for(int i = 0; i < n; i++){
				if(stus[i].id.substr(4, 6) == coms) mp[stus[i].id.substr(1, 3)]++; 
			}
			for(unordered_map<string, int>::iterator it = mp.begin(); it != mp.end(); it++){
				vs.push_back({it -> first, it -> second});
			}
		}
		if(com != 2){
			sort(vs.begin(), vs.end());
			for(int i = 0; i < vs.size(); i++){
				cout << vs[i].id << " " << vs[i].score << endl;
			}
		}
		if(!cnt && !vs.size()) cout << "NA" << endl;
	}
	return 0;
}