[数据结构与算法]pat甲级——1157 Anniversary (25 分)

代码：

#include<bits/stdc++.h>
using namespace std;

struct people {
    string id, birthday;
};

bool cmp(people a, people b) {
    return a.birthday < b.birthday;
}

int main() {
    int n;
    cin >> n;
    unordered_map<string, int> alumni;
    for(int i = 0; i < n; i++) {
        string temp;
        cin >> temp;
        alumni[temp] = 1;
    }
    int sum = 0;
    vector<people> participants;
    vector<people> alumniInParticipants;
    int m;
    cin >> m;
    for(int i = 0; i < m; i++) {
        string temp;
        cin >> temp;
        if(alumni.find(temp) != alumni.end()) {
            alumniInParticipants.push_back({temp, temp.substr(7, 7)});
        }
        participants.push_back({temp, temp.substr(7, 7)});
    }
    cout << alumniInParticipants.size() << endl;
    if(alumniInParticipants.size() != 0) {
        sort(alumniInParticipants.begin(), alumniInParticipants.end(), cmp);
        cout << alumniInParticipants[0].id << endl;
    }
    else {
        sort(participants.begin(), participants.end(), cmp);
        cout << participants[0].id << endl;
    }
    return 0;
}

总结：
spp中的substr是起始位置加长度