matrix_inverse.java

用QR分解来求矩阵的全部特征值 包括：QR分解

public class Matrix_Inverse {
	public static double[][] Inverse(double[][] a,int n){
		int i,j,k;
		for(i=0;i<n;i++){
			a[i][i]=1/a[i][i];
			for(j=0;j<n;j++)
				if(j!=i)
					a[i][j]=a[i][j]*a[i][i];
			for(k=0;k<n;k++)
				for(j=0;j<n;j++)
					if(k!=i && j!=i)
						a[k][j]=a[k][j]-a[k][i]*a[i][j];			
			for(k=0;k<n;k++)
				if(k!=i)
					a[k][i]=-a[k][i]*a[i][i];
		}
		for(i=0;i<n;i++){
			for(j=0;j<n;j++)
				System.out.print(a[i][j]+" ");
			System.out.println();
		}
		return a;
	}
	
/*	public static void main(String[] args){
		double[][] A={{1,2},{2,1}};
		double[][] A_inv;
		int n=A.length;
		A_inv=Inverse(A,n);		
	}*/

}