bzoj1013

这道题题解太多，只贴代码。

#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std ;  

const int MAXN = 50 ; 
double value [ MAXN ] [ MAXN ] ; 
double ans [ MAXN ] ;
int N ; 

void print () {
    for ( int i = 0 ; i < N ; ++ i ) {
        for ( int j = 0 ; j <= N ; ++ j ) printf ( "%.6lf " , value [ i ] [ j ] ) ;
        putchar ( '
' ) ;
    }
    putchar ( '
' ) ;
}

void Gauss () {
    for ( int i = 0 ; i < N ; ++ i ) {
        {
            int p = i ; 
            for ( int j = i + 1 ; j < N ; ++ j ) 
                if ( fabs ( value [ p ] [ i ] ) < fabs ( value [ j ] [ i ] ) ) p = j ;
            swap_ranges ( value [ i ] , value [ i ] + N + 1 , value [ p ] ) ;
        }
        {
            const double d = 1.0 / value [ i ] [ i ] ; 
            for ( int j = 0 ; j <= N ; ++ j ) value [ i ] [ j ] *= d ;
        }
        for ( int j = 0 ; j < N ; ++ j ) {
            if ( j == i ) continue ; 
            const double d = value [ j ] [ i ] ;
            for ( int k = 0 ; k <= N ; ++ k ) value [ j ] [ k ] -= d * value [ i ] [ k ] ;
        }
    }
}

double x [ MAXN ] [ MAXN ] ;
int main () {
    scanf ( "%d" , & N ) ;
    for ( int i = 0 ; i <= N ; ++ i ) 
        for ( int j = 0 ; j < N ; ++ j ) scanf ( "%lf" , & x [ i ] [ j ] ) ;
    for ( int i = 0 ; i < N ; ++ i ) x [ i ] [ N ] = 0.0 ;
    for ( int i = 0 ; i < N ; ++ i ) {
        for ( int j = 0 ; j < N ; ++ j ) {
            value [ i ] [ j ] = 2 * ( x [ i ] [ j ] - x [ i + 1 ] [ j ] ) ;
            value [ i ] [ N ] += x [ i ] [ j ] * x [ i ] [ j ] - x [ i + 1 ] [ j ] * x [ i + 1 ] [ j ] ;
        }
    }
    Gauss () ;
    printf ( "%.3lf" , value [ 0 ] [ N ] ) ;
    for ( int i = 1 ; i < N ; ++ i ) printf ( " %.3lf" , value [ i ] [ N ] ) ;
    return 0 ;
}