P5266 【深基17.例6】学籍管理(map)

首先要注意score的范围，所以要用long long int，其次OK两个字母都是大写，并且插入和修改后都要输出Ok

#include<iostream>
#include<set>
#include<map>
#define int long long
using namespace std;
signed main() {
	map<string, int>mapstudent;
	int n;
	cin >> n;
	while (n--) {
		int op;
		cin >> op;
		if (op == 1) {
			int score;
			string name;
			cin >> name >> score;
			auto it=mapstudent.find(name);
			if (it == mapstudent.end())mapstudent.insert(pair<string, int>(name, score)), cout << "OK" << endl;
			else it->second = score,cout<<"OK"<<endl;
		}
		if (op == 2) {
			string name;
			cin >> name;
			auto it = mapstudent.find(name);
			if (it == mapstudent.end())cout << "Not found" << endl;
			else cout << it->second << endl;
		}
		if (op == 3) {
			string name;
			cin >> name;
			auto it = mapstudent.find(name);
			if (it == mapstudent.end())cout << "Not found" << endl;
			else {
				mapstudent.erase(it);
				cout << "Deleted successfully" << endl;
			}
		}
		if (op == 4)cout << mapstudent.size() << endl;
	}
	return 0;
}