package Algorithms;

public class NaiveGaussianAlgorithm {

	public double[] Gaussian(double arr[][], double vector[]) {

		int n = vector.length;

		//forward elimination
		for(int k = 0; k < n; k++) {
			int max = k;

			for(int i = (k + 1); i < n; i++) {
				if(Math.abs(arr[i][k]) > Math.abs(arr[max][k])) {
					max = i;
				}
			}

			double[] temp = arr[k];
			arr[k] = arr[max];
			arr[max] = temp;

			double a = vector[k];
			vector[k] = vector[max];
			vector[max] = a;

			for (int i = k + 1; i < n; i++) {
				double factor = arr[i][k] / arr[k][k];
				vector[i] -= factor * vector[k];
				for(int j = k; j< n; j++) {
					arr[i][j] -= factor *arr[k][j];
				}
			}
		}

		//back substitution
		double vectorSolution[] = new double[n];
		vectorSolution[n] = vector[n] / arr[n][n];

		for(int i = n - 1;i >= 0; i--) {
			double sum = 0.0;
			for(int j = i + 1; j < n; j++) {
				sum += arr[i][j] * vectorSolution[j];
			}
			vectorSolution[i] =(vector[i] - sum) / arr[i][i];
		}

		return vectorSolution;
	}

	public void naiveGaussian(double arr[][], double vector[]) {

		System.out.println(Gaussian(arr, vector));
	}
}