【BZOJ 1013】【JSOI2008】球形空间产生器sphere 高斯消元基础题

#include<cmath>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define for1(i,a,n) for(int i=(a);i<=(n);++i)
#define for2(i,a,n) for(int i=(a);i<(n);++i)
#define for3(i,a,n) for(int i=(a);i>=(n);--i)
#define for4(i,a,n) for(int i=(a);i>(n);--i)
using namespace std;
double a[13][13],f[13];
int N;
inline double sqr(double x){return x*x;}
inline void swapp(double &d,double &b){double c=b;b=d;d=c;}
inline void gauss(){
    for1(i,1,N-1){
        int now=i;
        for1(j,i+1,N) if (fabs(a[now][i])<fabs(a[j][i])) now=j;
        for1(j,i,N+1) swapp(a[i][j],a[now][j]);
        for1(j,i+1,N){
            double chu=a[j][i]/a[i][i];
            for1(k,i,N+1) a[j][k]-=chu*a[i][k];
        }
    }
    for3(i,N,1){
        for1(j,i+1,N) a[i][N+1]-=a[i][j]*a[j][N+1];
        a[i][N+1]/=a[i][i];
    }
}
int main(){
    scanf("%d\n",&N);
    memset(a,0,sizeof(a));memset(f,0,sizeof(f));
    for1(i,1,N)scanf("%lf",&f[i]);
    for1(i,1,N)for1(j,1,N){
        double t; scanf("%lf",&t);
        a[i][j]=2*(t-f[j]);
        a[i][N+1]+=sqr(t)-sqr(f[j]);
    }gauss();
    for2(i,1,N) printf("%.3lf ",a[i][N+1]);
    printf("%.3lf\n",a[N][N+1]);
    return 0;
}