feat(matrix): Implement determinant calculation for square matrices

Author: Rony-2004

src/main/java/com/thealgorithms/matrix/MatrixDeterminant.java

@@ -0,0 +1,56 @@
+package com.thealgorithms.matrix;
+
+// Problem: Determinant of a Matrix
+// Description: Calculate the determinant of any square matrix using recursion.
+// URL: https://en.wikipedia.org/wiki/Determinant
+
+public final class MatrixDeterminant {
+
+    private MatrixDeterminant() {
+        // Prevent instantiation
+    }
+
+    public static double determinant(double[][] m) {
+        int n = m.length;
+        for (double[] row : m) {
+            if (row.length != n) {
+                throw new IllegalArgumentException("Matrix must be square");
+            }
+        }
+
+        if (n == 1) {
+            return m[0][0];
+        }
+
+        if (n == 2) {
+            return m[0][0] * m[1][1] - m[0][1] * m[1][0];
+        }
+
+        double det = 0;
+        for (int c = 0; c < n; c++) {
+            det += Math.pow(-1, c) * m[0][c] * determinant(minor(m, 0, c));
+        }
+        return det;
+    }
+
+    private static double[][] minor(double[][] m, int row, int col) {
+        int n = m.length;
+        double[][] min = new double[n - 1][n - 1];
+        int r = 0;
+
+        for (int i = 0; i < n; i++) {
+            if (i == row) {
+                continue;
+            }
+            int c = 0;
+            for (int j = 0; j < n; j++) {
+                if (j == col) {
+                    continue;
+                }
+                min[r][c++] = m[i][j];
+            }
+            r++;
+        }
+        return min;
+    }
+}

src/test/java/com/thealgorithms/matrix/MatrixDeterminantTest.java

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+package com.thealgorithms.matrix;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class MatrixDeterminantTest {
+
+    @Test
+    void test2x2Matrix() {
+        double[][] matrix = {{1, 2}, {3, 4}};
+        assertEquals(-2, MatrixDeterminant.determinant(matrix), 1e-9);
+    }
+
+    @Test
+    void test3x3Matrix() {
+        double[][] matrix = {{2, 0, 1}, {3, 0, 0}, {5, 1, 1}};
+        assertEquals(3, MatrixDeterminant.determinant(matrix), 1e-9);
+    }
+
+    @Test
+    void test1x1Matrix() {
+        double[][] matrix = {{5}};
+        assertEquals(5, MatrixDeterminant.determinant(matrix), 1e-9);
+    }
+
+    @Test
+    void testSingularMatrix() {
+        double[][] matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
+        assertEquals(0, MatrixDeterminant.determinant(matrix), 1e-9);
+    }
+
+    @Test
+    void testNonSquareMatrix() {
+        double[][] matrix = {{1, 2, 3}, {4, 5, 6}};
+        assertThrows(IllegalArgumentException.class, () -> MatrixDeterminant.determinant(matrix));
+    }
+}