zhuiganfa41.java

数值分析之计算方法与实验3：线性方程组数值解法 by java

import java.io.*;
class Zhuiganfa41{
	static void ZhuiGan(double[][] A,double[] b,int m)throws IOException{
  	PrintWriter out = new PrintWriter(new FileWriter("result.txt"));
		double [][]f=new double[m][m];
		double[]y=new double[m]; 
		double[]x=new double[m]; 
		f[0][0]=A[0][0];
		y[0]=b[0];
		for(int i=0;i<m-1;i++){
			f[i][i+1]=A[i][i+1];
		}
		for(int i=1;i<m;i++){
			f[i][i]=A[i][i]-(A[i][i-1]/f[i-1][i-1])*f[i-1][i];
			y[i]=b[i]-(A[i][i-1]/f[i-1][i-1])*y[i-1];
		}
		x[m-1]=y[m-1]/f[m-1][m-1];
		for(int i=m-2;i>=0;i--){
			x[i]=(y[i]-f[i][i+1]*x[i+1])/f[i][i];
		}
		for(int i=0;i<m;i++){
			out.println("x["+(i+1)+"]="+x[i]);
		}
		out.close();
	}
	public static void main(String [] args)throws IOException{
		int m=4;
		double [][] a={{2.0,-1.0,0.0,0.0},
		             {-1.0,2.0,-1.0,0.0},
		             {0.0,-1.0,2.0,-1.0},
		             {0.0,0.0,-1.0,2.0}};
		double []b={5.0,-12.0,11.0,-1.0};
		ZhuiGan(a,b,m);
	}
}