LeetCode 88: Merge Sorted Array

Given two sorted integer arrays A and B, merge B into A as one sorted array.
Note:
You may assume that A has enough space (size that is greater or equal to m + n) to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

public class Solution {
    public void merge(int A[], int m, int B[], int n) {
        // We don't use extra memory.
        // Reverse merge
        if (n == 0)
            return;
            
        if (m == 0)
            for (int i = 0; i < n; i++)
                A[i] = B[i];
        
        int i = m-1, j = n-1;
        
        for (int k = m+n-1; k>=0; k--)
        {
            if (i < 0)
                A[k] = B[j--];
            else if (j < 0)
                A[k] = A[i--];
            else if (A[i] >= B[j])
                A[k] = A[i--];
            else
                A[k] = B[j--];
        }
    }
}