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;
}