高斯消元模板啦啦啦..

放一下高斯消元模板啦啦啦..

    for ( i = 1; i <= n; i ++ ){        for ( j = i; j <= n; j ++ ){            if ( _abs ( fc[j][i] ) > eps ){                for ( k = i; k <= n+1; k ++ ){                    swap ( fc[j][k], fc[i][k] );                }                break;            }        }        for ( j = 1; j <= n; j ++ ){            if ( i != j && _abs (fc[j][i]) > eps ){                double tmp = fc[j][i]/fc[i][i];                for ( k = i; k <= n+1; k ++ ) fc[j][k] -= tmp*fc[i][k];            }        }    }    for ( i = 1; i <= n; i ++ ){        for ( j = 1; j <= n; j ++ ){            if ( _abs (fc[j][i]) > eps ) ans[i] = fc[j][n+1]/fc[j][i];        }    }