hdu 4576 概率dp＋滚动数组

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卡常数算什么本事．．．．．．．．真恶心，多做几个位运算都超时

#include <iostream>#include <cstring>#include <algorithm>#include <cstdio>#define MAX 207using namespace std;int n,m,l,r;double dp[2][MAX];int main ( ){    while ( ~scanf ( "%d%d%d%d" , &n , &m , &l , &r ) , n+m+l+r )    {        int w;        memset ( dp[0] , 0 , sizeof ( dp[0] ) );        dp[0][1] = 1.0;        int i = 1;        while ( m-- )        {            scanf ( "%d" , &w );            memset ( dp[i] , 0 , sizeof ( dp[i] ) );            for ( int j = 1 ; j <= n ; j++ )                if ( dp[i^1][j] )                    dp[i][((j-1)-w+n)%n+1] += 0.5*dp[i^1][j],                    dp[i][((j-1)+w)%n+1] += 0.5*dp[i^1][j];            i ^= 1;        }        double ans = 0.0;        for ( int j = l ; j <= r ; j++ )            ans += dp[i^1][j];        printf ( "%.4lf\n" , ans );    }}

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