[学习笔记]高斯消元

#include<iostream>
#include<cstring>
#include<cstdio>
#define N 110
using namespace std;
double a

,b
;bool vis
;
inline double gabs(const double &x)
{
return x>0?x:-x;
}
const double eps=0.00000001;
inline int dcmp(const double &x)
{
return gabs(x)<eps?0:(x>0?1:-1);
}
int main()
{
int n;scanf("%d",&n);
for(int i=1,x;i<=n;i++)
{
for(int j=1;j<=n;j++)
scanf("%d",&x),a[i][j]=x;
scanf("%d",&x),b[i]=x;
}
for(int i=1;i<=n;i++)
{
int t=i;double x,y;
for(int j=i;j<=n;j++)
if(gabs(a[j][i])>gabs(a[t][i])) t=j;
swap(a[i],a[t]),swap(b[i],b[t]),x=a[i][i];
if(!dcmp(x)) return !printf("No Solution\n");
for(int j=i;j<=n;j++) a[i][j]/=x;b[i]/=x;
for(int j=1;j<=n;j++)
if(j^i)
{
y=a[j][i],b[j]-=y*b[i];
for(int k=i;k<=n;k++)
a[j][k]-=y*a[i][k];
}
}
for(int i=1;i<=n;i++) printf("%.2f\n",b[i]);
return 0;
}