poj 3370 Halloween treats

http://poj.org/problem?id=3370

鸽巢原理

代码：

#include<iostream>

#include<cstdio>

#include<cstring>

#include<cmath>

#include<algorithm>

#include<vector>

#include<set>

#include<map>

#include<string>

#include<queue>

#include<stack>

#include <iomanip>

using namespace std;

#define LL long long

#define ULL unsigned long long

const double eps=1e-6;

const int INF=0x3f3f3f3f;

const int N=100005;

int a[N];

int f[N];

int main()

{

    //freopen("data.in","r",stdin);

    int n,m;

    while(scanf("%d %d",&n,&m)!=EOF)

    {

        if(n==0&&m==0)

        break;

        memset(f,-1,sizeof(f));

        for(int i=1;i<=m;++i)

        scanf("%d",&a[i]);

        int l,r;

        int k=0;

        f[k]=0;

        for(int i=1;i<=n;++i)

        {

            k=(k+a[i])%n;

            if(f[k]==-1)

            f[k]=i;

            else

            {l=f[k];r=i;break;}

        }

        for(int i=l+1;i<=r;++i)

        {

            printf("%d",i);

            if(i<r)

            printf(" ");

        }

        printf("\n");

    }

    return 0;

}