pat 1124 Raffle for Weibo Followers（20 分）

1124 Raffle for Weibo Followers（20 分）

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 <algorithm>
#include <cstdio>
#include <cstring>
#include <map>
#include <stack>
#include <vector>
#include <queue>
#include <set>
using namespace std;
const int MAX = 1e3 + 10;

int m, n, s, cnt = 0;
struct node
{
    char s[30];
}P[MAX], S[MAX];
set <string> st;
pair <set <string> :: iterator, bool> pr;
set <string> :: iterator iter;

int main()
{
//    freopen("Date1.txt", "r", stdin);
    scanf("%d%d%d", &m, &n, &s);
    for (int i = 1; i <= m; ++ i)
        scanf("%s", &P[i].s);

    for (int i = s; i <= m; i += n)
    {
        pr = st.insert(P[i].s);
        if (pr.second)
        {
            strcpy(S[cnt ++].s, P[i].s);
            continue;
        }
        while (i <= m)
        {
            ++ i;
            pr = st.insert(P[i].s);
            if (pr.second)
            {
                strcpy(S[cnt ++].s, P[i].s);
                break;
            }
        }
    }

    if (cnt == 0)
    {
        printf("Keep going...\n");
        return 0;
    }
    for (int i = 0; i < cnt; ++ i)
        printf("%s\n", S[i].s);
    return 0;
}