main.cpp

很有用的算法哦。这是我好不容易

#include<math.h>
#include<iostream.h>
const int N=3;
int gausdl(int n,double a[][N],double b[],double *&x,double eps){ 
	int i,j,u,v;
    double p,t,s,q;
    for (i=0; i<=n-1; i++)
      { u=i*n+i; p=0.0; x[i]=0.0;
        for (j=0; j<=n-1; j++)
          if (i!=j)
            { v=i*n+j; p=p+fabs(a[v]);}
        if (p>=fabs(a[u]))
          { cout<<"fail"<<endl; return(-1);}
      }
    p=eps+1.0;
    while (p>=eps)
      { p=0.0;
        for (i=0; i<=n-1; i++)
          { t=x[i]; s=0.0;
            for (j=0; j<=n-1; j++)
              if (j!=i) s=s+a[i*n+j]*x[j];
            x[i]=(b[i]-s)/a[i*n+i];
            q=fabs(x[i]-t)/(1.0+fabs(x[i]));
            if (q>p) p=q;
          }
      }
    return(1);
  }





  main()
  { int i;
    double eps;
    static double a[3][3]={ {6,-1,-1},{-1,6,-1},{-1,-1,6}};
    static double x[4],b[3]={11.33,32,42};
    eps=0.000001;
    if (gausdl(3,a,b,x,eps)>0)
      for (i=0;i<=2; i++)cout<<"x["<<i+1<<"]="<<x[i]<<endl;
  }