example2_6.java

清华大学2002年出版的《科学与工程数值计算算法Java》配套源码

import java.applet.*;
import java.awt.*;
public class Example2_6 extends Applet
{
  public static double  MdetGauss(double[][] a,int n)
  {int i,j,row,col,k;
   double max,temp,det=1;;
   for(k=0;k<n;k++)
   {//找主元
    max=0;row=col=k;
    for(i=k;i<n;i++)
     for(j=k;j<n;j++)
     {temp=Math.abs(a[i][j]);
      if(max<temp){max=temp;row=i;col=j;}
	  }
	//交换行列，将主元调整到k行k列上
	if(max==0)return 0;
	if(row!=k)
	{for(j=0;j<n;j++)
	 {temp=a[row][j];a[row][j]=a[k][j];a[k][j]=temp;}
	 }
	 if(col!=k)
	 {for(i=0;i<n;i++)
	   {temp=a[i][col];a[i][col]=a[i][k];a[i][k]=temp;}
	 }

	 det*=a[k][k];
	 for(j=k+1;j<n;j++)a[k][j]/=a[k][k];
	 for(j=k+1;j<n;j++)
	  for(i=k+1;i<n;i++)a[i][j]-=a[i][k]*a[k][j];
	 for(i=0;i<k;i++)a[i][k]=0;
	 a[k][k]=1;
  }
  return det;
 }

public void paint(Graphics g)
{double[][] a={{0.2368,0.2471,0.2568,1.2671},{1.1161,0.1254,0.1397,0.149},
               {0.1582,1.1675,0.1768,0.1871},{0.1968,0.2071,1.2168,0.2271}};
 double[][] b={{3,-3,-2,4},{5,-5,1,8},{11,8,5,-7},{5,-1,-3,-1}};
 double det;
 det=MdetGauss(a,3);
 g.drawString("Det(A)="+det,10,20);
 det=MdetGauss(b,4);
 g.drawString("Det(B)="+det,10,40);
 }
}