elimination.txt

利用消元法中的列主元消元法来实现线性方程组的求解

#include<stdio.h>
#include<math.h>
void main()
{
	int m,k,t,i,j,v,u;
	double a[9][9]={31,-13,0,0,0,-10,0,0,0,-13,35,-9,0,-11,0,0,0,0,0,-9,31,-10,0,0,0,0,0,0,0,-10,79,-30,0,0,0,-9,0,0,0,-30,57,-7,0,-5,0,0,0,0,0,-7,47,-30,0,0,0,0,0,0,0,-30,41,0,0,0,0,0,0,-5,0,0,27,-2,0,0,0,-9,0,0,0,2,-29};
	double	b[9]={-25,27,-23,0,-20,12,-7,7,10};
	double x[8];
	double tem=0,q,max;
	for(k=0;k<8;k++)
	{
		{
			max=fabs(a[k][k]);  m=k;
			for(u=k+1;u<9;u++)
				if(fabs(a[u][k])>max)
				{
					m=u;
					max=fabs(a[u][k]);
				}
			for(v=k;v<9;v++)
			{
				t=a[k][v];  a[k][v]=a[m][v];  a[m][v]=t;
			}
				t=b[k];     b[k]=b[m];        b[m]=t;
		}
		for(i=k+1;i<9;i++)
		{
			q=a[i][k]/a[k][k];
			for(j=k+1;j<9;j++)
				a[i][j]=a[i][j]-q*a[k][j];
			b[i]=b[i]-q*b[k];
			
		}
	}
	
	x[8]=b[8]/a[8][8];
	printf("%lf,%lf\n",x[8],b[8]);
	for(i=7;i>=0;i--)
	{
		for(j=i+1;j<=8;j++)
		{
			//printf("%lf ",a[i][j]);
			tem+=a[i][j]*x[j];
		}
		x[i]=(b[i]-tem)/a[i][i];
		tem=0;
	}
	for(i=0;i<=8;i++)
		printf("%lf\n",x[i]);
}