Matrix_Determinant.java

import java.util.*;

class determinant
{
 
    // Dimension of input square matrix
    static final int N = 4;
 
    // Function to get determinant of matrix
    static int determinantOfMatrix(int mat[][], int n)
    {
        int num1, num2, det = 1, index, total = 1;
 
        // temporary array for storing row
        int[] temp = new int[n + 1];
 
        // loop for traversing the diagonal elements
        for (int i = 0; i < n; i++)
        {
            index = i;
 
            // finding the index which has non zero value
            while (mat[index][i] == 0 && index < n)
            {
                index++;
            }
            if (index == n) // if there is non zero element the determinant of matrix is zero
            {
                continue;
            }
            if (index != i)
            {
                // loop for swaping the diagonal element row and index row
                for (int j = 0; j < n; j++)
                {
                    swap(mat, index, j, i, j);
                }
                det = (int)(det * Math.pow(-1, index - i));
            }
 
            for (int j = 0; j < n; j++)
            {
                temp[j] = mat[i][j];
            }
 
            for (int j = i + 1; j < n; j++)
            {
                num1 = temp[i];
                num2 = mat[j][i];

                for (int k = 0; k < n; k++)
                {
                    mat[j][k] = (num1 * mat[j][k])- (num2 * temp[k]);
                }
                total = total * num1;
            }
        }
 
        // multiplying the diagonal elements to get
        // determinant
        for (int i = 0; i < n; i++)
        {
            det = det * mat[i][i];
        }
        return (det / total);
    }
 
    static int[][] swap(int[][] arr, int i1, int j1, int i2, int j2)
    {
        int temp = arr[i1][j1];
        arr[i1][j1] = arr[i2][j2];
        arr[i2][j2] = temp;
        return arr;
    }
 
    public static void main(String[] args)
    {
 
        int mat[][] = { { 1, 0, 2, -1 },
                        { 3, 0, 0, 5 },
                        { 2, 1, 4, -3 },
                        { 1, 0, 5, 0 } };
 
        System.out.printf(
            "Determinant of the matrix is : %d",
            determinantOfMatrix(mat, N));
    }
}