Java/src/test/java/com/thealgorithms/divideandconquer/StrassenMatrixMultiplicationTest.java

package com.thealgorithms.divideandconquer;

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.Test;

class StrassenMatrixMultiplicationTest {

    StrassenMatrixMultiplication SMM = new StrassenMatrixMultiplication();

    // Strassen Matrix Multiplication can only be allplied to matrices of size 2^n
    // and has to be a Square Matrix

    @Test
    public void StrassenMatrixMultiplicationTest2x2() {
        int[][] A = { { 1, 2 }, { 3, 4 } };
        int[][] B = { { 5, 6 }, { 7, 8 } };
        int[][] expResult = { { 19, 22 }, { 43, 50 } };
        int[][] actResult = SMM.multiply(A, B);
        assertArrayEquals(expResult, actResult);
    }

    @Test
    void StrassenMatrixMultiplicationTest4x4() {
        int[][] A = { { 1, 2, 5, 4 }, { 9, 3, 0, 6 }, { 4, 6, 3, 1 }, { 0, 2, 0, 6 } };
        int[][] B = { { 1, 0, 4, 1 }, { 1, 2, 0, 2 }, { 0, 3, 1, 3 }, { 1, 8, 1, 2 } };
        int[][] expResult = { { 7, 51, 13, 28 }, { 18, 54, 42, 27 }, { 11, 29, 20, 27 }, { 8, 52, 6, 16 } };
        int[][] actResult = SMM.multiply(A, B);
        assertArrayEquals(expResult, actResult);
    }

    @Test
    void StrassenMatrixMultiplicationTestNegetiveNumber4x4() {
        int[][] A = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 }, { 13, 14, 15, 16 } };
        int[][] B = { { 1, -2, -3, 4 }, { 4, -3, -2, 1 }, { 5, -6, -7, 8 }, { 8, -7, -6, -5 } };
        int[][] expResult = { { 56, -54, -52, 10 }, { 128, -126, -124, 42 }, { 200, -198, -196, 74 },
                { 272, -270, -268, 106 } };
        int[][] actResult = SMM.multiply(A, B);
        assertArrayEquals(expResult, actResult);
    }

}