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Posted in : Java Magazine

Here is my code:

import java.util.Scanner; import java.util.*; public class gausselimination { private static final double EPSILON = 1e-10; int n;int N; double A[][]; double B[]; public double[] lsolve(double[][] A, double[] B) { for (int p = 0; p < n; p++) { int max = p; for (int i = p + 1; i < N; i++) { if (Math.abs(A[i][p]) > Math.abs(A[max][p])) { max = i; } } double[] temp = A[p]; A[p] = A[max]; A[max] = temp; double t = B[p]; B[p] = B[max]; B[max] = t; if (Math.abs(A[p][p]) <= EPSILON) { throw new RuntimeException("Matrix is singular or nearly singular"); } for (int i = p + 1; i < N; i++) { double alpha = A[i][p] / A[p][p]; B[i] -= alpha * B[p]; for (int j = p; j < n; j++) { A[i][j] -= alpha * A[p][j]; } } } double[] x = new double[n]; for (int i = n - 1; i >= 0; i--) { double sum = 0.0; for (int j = i + 1; j < n; j++) { sum += A[i][j] * x[j]; } x[i] = (B[i] - sum) / A[i][i]; } System.out.println("the values of unknowns are:-"); for (int i = 0; i < n; i++) System.out.println("x" + i + " " +x[i]); return x; } public void input() { double k; Scanner s=new Scanner(System.in); System.out.println("enter no of equations "); N = s.nextInt(); A = new double[N][]; System.out.println("enter no of unknowns"); n=s.nextInt(); for(int l=0;l<N;l++){ A[l]= new double[n]; } System.out.println("enter the co-efficient of equations"); for(int i=0;i<N;i++){ System.out.println("enter the co-efficient of equation "+ (i+1)); for(int j=0;j<n;j++){ k=s.nextDouble(); A[i][j]=k; }} B = new double[N]; System.out.println("enter the RHS side of equations"); for(int i=0;i<N;i++){ System.out.println("enter the RHS of equation "+ (i+1)); k=s.nextDouble(); B[i]=k; } } public static void main(String args[]) { gausselimination g = new gausselimination(); g.input(); g.lsolve(g.A, g.B); } }

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