Method fft

src/test/java/com/thealgorithms/maths/FFTTest.java:116–137

()

    // https://scistatcalc.blogspot.com/2013/12/fft-calculator.html used this link to
    // ensure the result
    @Test
    void fft() {
        ArrayList<FFT.Complex> arr = new ArrayList<FFT.Complex>();
        FFT.Complex complex1 = new FFT.Complex(2.0, 2.0);
        FFT.Complex complex2 = new FFT.Complex(1.0, 3.0);
        FFT.Complex complex3 = new FFT.Complex(3.0, 1.0);
        FFT.Complex complex4 = new FFT.Complex(2.0, 2.0);

        arr.add(complex1);
        arr.add(complex2);
        arr.add(complex3);
        arr.add(complex4);
        arr = FFT.fft(arr, false);
        double realV1 = arr.get(0).getReal();
        double realV2 = arr.get(2).getReal();
        double imgV1 = arr.get(0).getImaginary();
        double imgV2 = arr.get(2).getImaginary();
        assertEquals(8.0, realV1);
        assertEquals(2.0, realV2);
        assertEquals(8.0, imgV1);
        assertEquals(-2.0, imgV2);
    }
}