public void mergeSortedArray(int[] A, int m, int[] B, int n) {
        // write your code here
        int indexA = m-1, indexB = n-1, index = m + n - 1;
        while (indexA >= 0 && indexB >= 0) {
            if (A[indexA] > B[indexB]) {
                A[index--] = A[indexA--];
            } else {
                A[index--] = B[indexB--];
            }
        }
        while (indexA >= 0) {
            A[index--] = A[indexA--];
        }
        while (indexB >= 0) {
            A[index--] = B[indexB--];
        }
    }