hdu3853[LOOPS] 继续浅尝期望概率DP

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f ( i , j ) 表示到（i，j）这个位置的期望
f ( i , j ) =( f (i+1,j)p1 + f(i,j+1) p2 + 2 ) / p3

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const int N = 1010 ;const int Inf = 1e9;double p0 [N] [N] , p1 [N] [N] , p2 [N] [N] , f [N] [N] ;int n , m ;int main () {    while (~scanf ( "%d%d" , & n , & m )) {        memset ( f , 0 , sizeof f ) ;        for ( int i = 1 ; i <= n ; ++ i )             for ( int j = 1 ; j <= m ; ++ j ) {                scanf ( "%lf" , & p0 [i] [j] ) ;                scanf ( "%lf" , & p1 [i] [j] ) ;                scanf ( "%lf" , & p2 [i] [j] ) ;            }        for ( int i = n ; i >= 1 ; -- i )             for ( int j = m ; j >= 1 ; -- j ) {                if ( i == n && j == m ) continue ;                if ( p0 [i] [j] == 1.0 ) continue ;                f [i] [j] = ( f [i+1] [j] * p2 [i] [j] + f [i] [j+1] * p1 [i] [j] + 2.0 ) / ( 1 - p0 [i] [j] ) ;            }        printf ( "%.3lf\n" , f [1] [1] ) ;    }    return 0 ; }

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