弱菜的各种模板

Posted 2021-01-10 cx233666

高斯-约当消元（这里以JSOI2008球形空间产生器）

#include<cmath>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define gt getchar()
#define ll long long
#define db double
#define File(s) freopen(s".in","r",stdin),freopen(s".out","w",stdout)
inline int in()
{
    int k=0;char ch=gt;
    while(ch<'-')ch=gt;
    while(ch>'-')k=k*10+ch-'0',ch=gt;
    return k;
}
db a[15][15];
int p[15],o[15];
const db eps=1e-3;
int main()
{
    int n=in()+1;
    for(int i=1;i<=n;++i)
    {
        for(int j=1;j<n;++j)
            scanf("%lf",a[i]+j),a[i][n+1]+=a[i][j]*a[i][j],a[i][j]*=2;
        a[i][n]=1;
    }   
    for(int i=1;i<=n;++i)
    {
        for(int j=1;j<=n;++j)if(!o[j]&&fabs(a[j][i])>eps){p[i]=j;break;}
        double t=a[p[i]][i];o[p[i]]=1;
        for(int j=1;j<=n+1;++j)a[p[i]][j]/=t;
        for(int k=1;k<=n;++k)
        {
            if(p[i]==k)continue;
            t=a[k][i];
            for(int j=1;j<=n+1;++j)a[k][j],a[k][j]-=a[p[i]][j]*t;
        }
    }
    for(int i=1;i<n;++i)printf("%.3lf ",a[p[i]][n+1]);puts("");
    return 0;
}