1 #include <stdio.h> 2 #include <string.h> 3  4 double answ[ 51 ] = { 5     0.0000,0.6667,0.0000,0.4074,0.0000, 6     0.3361,0.0000,0.2928,0.0000,0.2629, 7     0.0000,0.2407,0.0000,0.2233,0.0000, 8     0.2092,0.0000,0.1975,0.0000,0.1875, 9     0.0000,0.1789,0.0000,0.1714,0.0000,10     0.1648,0.0000,0.1589,0.0000,0.1536,11     0.0000,0.1487,0.0000,0.1443,0.0000,12     0.1403,0.0000,0.1366,0.0000,0.1332,13     0.0000,0.1300,0.0000,0.1270,0.0000,14     0.1243,0.0000,0.1217,0.0000,0.1192};15 16 /*17 18 double maps[ 100 ][ 100 ][ 100 ];19 short  dxdy[ 4 ][ 2 ] = {1,0,0,1,-1,0,0,-1};20 21 void madelist()    // 打表程序 22 {23     for ( int n = 1 ; n < 100 ; n += 2 ) {24         double sum = 0.0;25         memset( maps, 0, sizeof( maps ) );26         maps[ 0 ][ n/2 ][ n/2 ] = 1.0;27         for ( int t = 0 ; t < n ; ++ t )28         for ( int i = 0 ; i < n ; ++ i )29         for ( int j = 0 ; j < n ; ++ j )30         for ( int k = 0 ; k < 4 ; ++ k ) {31             int x = i+dxdy[ k ][ 0 ];32             int y = j+dxdy[ k ][ 1 ];33             if ( x > 0 && x < n-1 && y > 0 && y < n-1 )34                 maps[ t+1 ][ i ][ j ] += 0.25*maps[ t ][ x ][ y ];35             else if ( ( x == 0 && y == 0 ) || ( x == 0 && y == n-1 ) ||36                     ( x== n-1 && y == 0 ) || ( x == n-1 && y == n-1 ) )37                 maps[ t+1 ][ i ][ j ] += 0.5*maps[ t ][ x ][ y ];38             else maps[ t+1 ][ i ][ j ] += 1.0/3*maps[ t ][ x ][ y ];39             if ( i == n/2 && j == t ) {40                 sum += maps[ t+1 ][ i ][ j ];41                 maps[ t+1 ][ i ][ j ] = 0.0;42             }43         }44         printf("%.4lf,",sum);45     }46 }47 */48 49 int main()50 {51     int m;52     while ( ~scanf("%d",&m) ) 53         printf("%.4lf\n",answ[ m/2 ]);54     return 0;55 }