Added cofactor function

src/test/java/com/mattrixwv/matrix/TestIntegerMatrix.java

@@ -1113,4 +1113,62 @@ public class TestIntegerMatrix{
 		});
 		assertEquals("IntegerMatrix 10x10 failed determinant2", -10000000, matrix.determinant());
 	}
+
+	@Test
+	public void testCofactor(){
+		//1x1
+		IntegerMatrix matrix = new IntegerMatrix(grid1);
+		IntegerMatrix correctMatrix = new IntegerMatrix(grid1);
+		assertEquals("IntegerMatrix 1x1 failed cofactor", correctMatrix, matrix.cofactor());
+
+		//2x2
+		matrix = new IntegerMatrix(grid2);
+		correctMatrix = new IntegerMatrix(new int[][]{
+			{2, -1},
+			{-2, 1}
+		});
+		assertEquals("IntegerMatrix 2x2 failed cofactor", correctMatrix, matrix.cofactor());
+
+		//3x3
+		matrix = new IntegerMatrix(grid3);
+		correctMatrix = new IntegerMatrix(3, 3, 0);
+		assertEquals("IntegerMatrix 3x3 failed cofactor1", correctMatrix, matrix.cofactor());
+		matrix = new IntegerMatrix(new int[][]{
+			{1, 4, 2},
+			{2, 4, 1},
+			{4, 1, 2}
+		});
+		correctMatrix = new IntegerMatrix(new int[][]{
+			{7, 0, -14},
+			{-6, -6, 15},
+			{-4, 3, -4}
+		});
+		assertEquals("IntegerMatrix 3x3 failed cofactor2", correctMatrix, matrix.cofactor());
+
+		//4x4
+		matrix = new IntegerMatrix(grid4);
+		correctMatrix = new IntegerMatrix(4, 4, 0);
+		assertEquals("IntegerMatrix 4x4 failed cofactor1", correctMatrix, matrix.cofactor());
+		matrix = new IntegerMatrix(new int[][]{
+			{1, 2, 3, 4},
+			{2, 3, 4, 1},
+			{3, 4, 1, 2},
+			{4, 1, 2, 3}
+		});
+		correctMatrix = new IntegerMatrix(new int[][]{
+			{-36, 4, 4, 44},
+			{4, 4, 44, -36},
+			{4, 44, -36, 4},
+			{44, -36, 4, 4}
+		});
+		assertEquals("IntegerMatrix 4x4 failed cofactor2", correctMatrix, matrix.cofactor());
+
+		//10x10
+		//?Skipping 10x10 test because test took > 5s by itself
+		/*
+		matrix = new IntegerMatrix(grid10);
+		correctMatrix = new IntegerMatrix(10, 10, 0);
+		assertEquals("IntegerMatrix 10x10 failed cofactor1", correctMatrix, matrix.cofactor());
+		*/
+	}
 }