Method reverse

solution/0400-0499/0484.Find Permutation/Solution.java:20–26

(int[] arr, int i, int j)

    }

    private void reverse(int[] arr, int i, int j) {
        for (; i < j; ++i, --j) {
            int t = arr[i];
            arr[i] = arr[j];
            arr[j] = t;
        }
    }
}