import java.applet.*;
 import java.awt.*;
 public class Example2_9 extends Applet
{  public static boolean LU(double[][] a,int n)
  { int i,j,k;
    if (a[0][0]==0)return false;
    for(i=1;i<n;i++)a[i][0]/=a[0][0];
    for(i=1;i<n;i++)
    { for(k=0;k<i;k++)a[i][i]-=a[i][k]*a[k][i];
      if(a[k][k]==0)return false;
	  for(j=i+1;j<n;j++)
	    { for(k=0;k<i;k++)a[i][j]-=a[i][k]*a[k][j];
	      for(k=0;k<i;k++)a[j][i]-=a[j][k]*a[k][i];
	      a[j][i]/=a[i][i];
	    }
	}
      return true;
  }

  public void paint(Graphics g)
  {double[][] a={{2,4,4,2},{3,3,12,6},{2,4,-1,2},{4,2,1,1}};
   double[][] l=new double[4][4];
   int i,j;
   if(LU(a,4))
   {for(i=0;i<4;i++)
      {for(j=0;j<i;j++){l[i][j]=a[i][j];a[i][j]=0;}
        l[i][i]=1;}
    g.drawString("下三角L為：",10,20);
    g.drawString(""+l[0][0]+"  "+l[0][1]+"  "+l[0][2]+"  "+l[0][3],10,40);
	g.drawString(""+l[1][0]+"  "+l[1][1]+"  "+l[1][2]+"  "+l[1][3],10,60);
	g.drawString(""+l[2][0]+"  "+l[2][1]+"  "+l[2][2]+"  "+l[2][3],10,80);
    g.drawString(""+l[3][0]+"  "+l[3][1]+"  "+l[3][2]+"  "+l[3][3],10,100);
    g.drawString("上三角U為:",10,120);
	g.drawString(""+a[0][0]+"  "+a[0][1]+"  "+a[0][2]+"  "+a[0][3],10,140);
    g.drawString(""+a[1][0]+"  "+a[1][1]+"  "+a[1][2]+"  "+a[1][3],10,160);
    g.drawString(""+a[2][0]+"  "+a[2][1]+"  "+a[2][2]+"  "+a[2][3],10,180);
    g.drawString(""+a[3][0]+"  "+a[3][1]+"  "+a[3][2]+"  "+a[3][3],10,200);}
    else g.drawString("矩陣無法分解",10,20);
  }

}