PAT--1124. Raffle for Weibo Followers

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…

题解

#include <iostream>#include <string>#include <algorithm>#include <vector>#include <cstring>#include <cstdio>#include <set>using namespace std;const int maxn = 1000 + 5;int m, n, s;string candidates[maxn];int main(){#ifndef ONLINE_JUDGEfreopen("data.in", "r", stdin);#endif // ONLINE_JUDGE    cin >> m >> n >> s;    for(int i = 1; i <= m; ++i){        cin >> candidates[i];    }    vector<string> ans;    set<string> Set;    for(int i = s; i <= m;){        if(Set.count(candidates[i]) == 0){            ans.push_back(candidates[i]);            Set.insert(candidates[i]);            i += n;        }else{            i++;        }    }    if(ans.empty()) cout << "Keep going..." << endl;    else{        for(string s : ans) cout << s << endl;    }    return 0;}