HDU 4405（概率dp）

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#pragma warning(disable:4996)#include<cstdio>#include<cstring>#include<string>#include<cmath>#include<vector>#include<algorithm>#include<iostream>using namespace std;const int INF = 0x3f3f3f3f;const int MAXN = 100010;double dp[MAXN];int Hash[MAXN];int main(){    int N, M;    while (cin >> N >> M,N||M)    {        memset(dp, 0, sizeof(dp));        memset(Hash, -1, sizeof(Hash));        dp[N] = 0;        for (int i = M; i >= 1; i--)        {            int a, b;            cin >> a >> b;            Hash[a] = b;        }        for (int i = N - 1; i >= 0; i--)        {            if (Hash[i] == -1)            {                for (int k = 1; k <= 6; k++)                {                    dp[i] += dp[i+k] * (1.0 / 6.0);                }                dp[i] += 1;            }            else            {                dp[i] = dp[Hash[i]];            }        }        printf("%.4f\n", dp[0]);    }    return 0;}

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