// <APPLET CODE="PartPiv.class" WIDTH=367 HEIGHT=100>
// </APPLET>
import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class PartPiv extends Applet{
	MyFrame window;
	TextField ta;
	Panel P_control, P_bottom;
	Checkbox hilbert;

  public static void main(String args[]) {
	PartPiv bob = new PartPiv();
	bob.show();
	bob.init();
  }

  public void init () {
	P_control =  new Panel();
	P_bottom = new Panel();
	Color C_gray = new Color(150,150,150);
	Color C_gray2 = new Color(120,120,120);

	this.setLayout(new BorderLayout());
	P_bottom.setLayout(new GridLayout(3,1));
	P_bottom.setBackground(C_gray);
	P_control.setBackground(C_gray2);
	ta = new TextField(5);

	P_control.add(new Label("Number of equations"));
	P_control.add(ta);
	P_control.add(new Button("Enter Equations"));
	CheckboxGroup cbg = new CheckboxGroup();

	hilbert = new Checkbox("Hilbert Matrix",cbg,false);
	P_bottom.add(new Label("Matrix Created From"));
	P_bottom.add(new Checkbox("User input",cbg,true));
	P_bottom.add(hilbert);

	add("North",P_control);
	add("Center",P_bottom);	
  }
  public boolean action(Event evt, Object arg) {
	if (evt.target instanceof Button){
		int cellNum=1;
		cellNum = Integer.parseInt(ta.getText());
		if (cellNum > 15)
			cellNum = 15;
		window = new MyFrame("Equation Input",cellNum,hilbert.getState());
	}
	return true;
  }
}// End class
/////////////////////////////////////////////

class MyFrame extends Frame{
   Panel main_P, bot_P;
   double a[][];
   TextField ta[][];
   int n, cellNum;

   public MyFrame(String s,int cellNum, boolean fillBert) {
	super(s);
	setBackground(new Color(150,150,150));
	main_P = new Panel();
	this.cellNum = cellNum;

	main_P.setLayout(new GridLayout(cellNum,(cellNum+1)*2));
	this.setLayout(new BorderLayout());
	add("South",new Button("Done"));
	add("Center",main_P);

	takeInput(cellNum);
	fillHillbert(cellNum, fillBert);

	if (cellNum > 5)
		resize(cellNum*60,((cellNum+1)*2)*15);
	else
		resize(cellNum*80,((cellNum+1)*2)*20);
	if (cellNum == 1)
		resize(150,150);
	show();
   }
   public void takeInput(int num) {
	n = num;
	a = new double [n+1][n+2];
	ta = new TextField [n+1][n+2];
	// loop inputs the matrix data
  	for (int i =1;i<=n;i++) {
	    for (int j=1; j <= n+1;j++) {
		main_P.add(new Label(""+(i)+","+(j)+":"));
		ta[i][j] = new TextField();
		main_P.add(ta[i][j]);
	    }
	 }
   } // End takeInput()
   public void fillHillbert(int n, boolean state) {
	if (state) {
	for (int i = 1; i <=n;i++) {
		for (int j =1 ; j <= n;j++) {
			ta[i][j].setText("1/"+(i+j-1));
		}
		ta[i][n+1].setText("0");
	}
	ta[1][n+1].setText("1");
	ta[1][1].setText("1");
   }
  }
  public boolean action(Event evt, Object arg) {
	if (evt.target instanceof Button){
		hide();
		// 1/2x + y = 2
		// 2x + 4y  = 8x
	  	for (int i =1;i<=n;i++) {
		    for (int j=1; j <= n+1;j++) {
			a[i][j] = checkFraction(ta[i][j].getText());
			System.out.println("ij "+a[i][j]);
		    }
		 }
		doPiv();
		double b [] = new double [cellNum+1];
		for (int i = 1; i <= cellNum;i++) {
			b[i]=a[i][cellNum+1];
		}
		new AnswerFrame("Solutions",b,cellNum);

	}
	return true;
  }
  public double checkFraction(String s) {
	String tempNoSpace="";
	for (int i = 0; i < s.length();i++) {
		if (s.charAt(i) != ' ')
			tempNoSpace += s.charAt(i);	
	}
	s = tempNoSpace;
	for (int i = 0; i < s.length();i++) {
		if (s.charAt(i) == '/') {
			String tempS="";
			for (int j=0;j<i;j++) {
				tempS += s.charAt(j);	
			}
			String tempS2 = "";
			for (int j=i+1;j<s.length();j++) {
				tempS2 += s.charAt(j);	
			}
			double a = Double.valueOf(tempS).doubleValue();
			double b = Double.valueOf(tempS2).doubleValue();
			return (a / b);
		}
	}
	return (Double.valueOf(s).doubleValue());
  }
/////////
public void doPiv() {
int count=0;
//next loop and the following 2 statements put the matrix system in
//diagonal form with 1's on the diagonal
for (int i=1;i<=n-1;i++) {
   double m = Math.abs(a[i][i]);
   int c = i;
   // next loop finds the highest element down the column
   for (int j=i+1;j<=n;j++) {
	if (Math.abs(a[j][i])> m) {
         m = Math.abs(a[j][i]);
         c = j;
	}
   } // end for j
   //next loop interchanges rows i and c
   for (int j=i;j<=n+1;j++) {
      double d = a[i][j];
	a[i][j] = a[c][j];
	a[c][j] = d;
		count++;
   } // end for j
   //next loop divids row i by a(i,i)
   for (int j=n+1;j >= i; j--) {
	a[i][j] = a[i][j] / a[i][i];
   } // end for j
   //next loop subracts appropriate multiples of row i from rows below
   for (int j=i+1;j<=n;j++) {
	for (int k=n+1; k >= i; k--) {
	   a[j][k] = a[j][k] - a[j][i] * a[i][k];
	} //end for k
   } // End for j
} //end for i

//next two statements fix the last row
a[n][n+1] = a[n][n+1]/a[n][n];
a[n][n]=1;
//next loop transforms the triangular matrix to the identity matrix
//plus a column (the last column) which is the solution vector
for (int i=n;i>=2; i--) {
   for (int k=i-1;k>=1;k--){
	for (int j=n+1;j>=i;j--) {
		System.out.println("value8 "+a[k][j]+" N: "+n);
	   a[k][j] = a[k][j] - a[k][i]*a[i][j];
		System.out.println("value9 "+a[k][j]);

	}
   }
}
//next loop prints the solution
for (int i=1;i<=n;i++) {
   System.out.println("x"+i+" is equal to "+a[i][n+1]);
}
}

///////
} // End class

////////////////////////
class AnswerFrame extends Frame{
   Panel main_P, bot_P;
   double a[][];
   TextField ta[][];
   int n;

   public AnswerFrame(String s,double []a, int cellNum) {
	super(s);
	main_P = new Panel();
	
	main_P.setLayout(new GridLayout(cellNum,1));
	this.setLayout(new BorderLayout());
	add("South",new Button("Done"));
	add("Center",main_P);

	if (cellNum > 5)
		resize(150,((cellNum+1)*2)*15);
	else
		resize(150,((cellNum+1)*2)*20);
	if (cellNum == 1)
		resize(150,150);
	char c_Var='x';
	c_Var -= 1;
	if (cellNum > 3) {
		c_Var -= cellNum;
		c_Var += 3;
	}
	for (int i=1; i <= cellNum;i++) {
		main_P.add(new Label(""+(char)(c_Var+i)+" = "+a[i]));
 	}
	show();
   }

  public boolean action(Event evt, Object arg) {
	if (evt.target instanceof Button){
		hide();
	}
	return true;
  }
///////
} // End class AnswerFrame