public static int[] invertPermutation(int... input){
        int[] target = new int[input.length];

        for(int i = 0 ; i < input.length ; i++){
            target[input[i]] = i;
        }

        return target;
    }
@Test
    public void testInvertPermutationInt(){
        assertArrayEquals(
                new int[]{ 2, 4, 3, 0, 1 },
                ArrayUtil.invertPermutation(3, 4, 0, 2, 1)
                );
    }