PTA 乙级 1055 集体照 (25分) C++

 好难啊,困了

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

int main()
{
    int n, k, m, h;
    cin >> n >> k;
    m = n / k;
    vector<pair<string,int>>student(n);
    for (int i = 0; i < n; i++)
        cin>>student[i].first>>student[i].second;
    sort(student.begin(), student.end(), [](pair<string,int>& a, pair<string, int>& b) {
        return a.second != b.second ? a.second < b.second : a.first > b.first;});
    bool flag = true;
    for (int i = (k - 1) * m; i >= 0; i -= m){
        int num = m;
        if (flag){
            num = n - i;
            flag = false;
        }
        int s = num % 2 ? 2 : 1;
        int e = num % 2 ? 1 : 2;
        for (int j = s; j < num; j += 2)
            cout << student[i + j - 1].first << " ";
        for (int j = num; j >= e; j -= 2)
            cout << student[i + j - 1].first<<(j > e?" ":"");
        cout << endl;
    }
    return 0;
}