1124. Raffle for Weibo Followers (20)

John got a full mark on PAT. He was so happy that he decided to hold a raffle（抽奖） for his followers on Weibo -- that is, he would select winners from every N followers who forwarded his post, and give away gifts. Now you are supposed to help him generate the list of winners.

Input Specification:

Each input file contains one test case. For each case, the first line gives three positive integers M (<= 1000), N and S, being the total number of forwards, the skip number of winners, and the index of the first winner (the indices start from 1). Then M lines follow, each gives the nickname (a nonempty string of no more than 20 characters, with no white space or return) of a follower who has forwarded John's post.

Note: it is possible that someone would forward more than once, but no one can win more than once. Hence if the current candidate of a winner has won before, we must skip him/her and consider the next one.

Output Specification:

For each case, print the list of winners in the same order as in the input, each nickname occupies a line. If there is no winner yet, print "Keep going..." instead.

Sample Input 1:

9 3 2
Imgonnawin!
PickMe
PickMeMeMeee
LookHere
Imgonnawin!
TryAgainAgain
TryAgainAgain
Imgonnawin!
TryAgainAgain

Sample Output 1:

PickMe
Imgonnawin!
TryAgainAgain

Sample Input 2:

2 3 5
Imgonnawin!
PickMe

Sample Output 2:

Keep going...

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

int main(){
    int m, n, s;
    string st;
    cin >> m >> n >> s;
    vector<string> v;
    map <string, bool> ma;
    for (int i = 0; i < m; i++) {
        cin >> st;
        v.push_back(st);
    }
    for (int i = s-1; i < v.size(); i = i + n) {
        while(ma[v[i]]){
            i++;
        }
        cout << v[i] << endl;
        ma[v[i]] = true;
    }
    if(m < s) cout << "Keep going...\n";
    
    return 0;
}