hdu 4405概率dp

#include <cstdio>
#include <cstring>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <queue>
#include <vector>
using namespace std;

const int maxe = ;
const int maxn = ;
const int INF  = 0x3f3f3f;

double dp[maxn];
int map[maxn];

int main()
{
    //freopen("E:\\acm\\input.txt","r",stdin);
    int N,M;
    while(cin>>N>>M && N+M){
        for(int i=N;i<=N+;i++) dp[i] = ;
        memset(map,,sizeof(map));
        for(int i=;i<=M;i++){
            int x,y;
            scanf("%d %d",&x,&y);
            map[x] = y;
        }
        for(int i=N-;i>=;i--){
            if(map[i]){
                dp[i] = dp[map[i]];
                continue;
            }
            int a[];
            double sum = ;
            for(int j=;j<=;j++){
                a[j] = i+j;
                while(map[a[j]]){
                    a[j] = map[a[j]];
                }
                sum += dp[a[j]] + ;
            }
            dp[i] = sum/;
        }
        printf("%.4lf\n",dp[]);
    }
}