Merge Sorted Array [LeetCode]

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 to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

Summary: It's easy, but should be careful about corner cases, like m is 0, n is 0. 

    void merge(int A[], int m, int B[], int n) {
        if(n == 0)
            return;
        if(m == 0) {
            memcpy(A, B, n * sizeof(B[0]));
            return;
        }
        int a = 0;
        int b = 0;
        int a_idx = 0;
        int new_len = m;
        while(true) {
            if(A[a] >= B[b]) {
                //insert B[b] before A[a]
                for(int i = new_len; i >= a + 1; i --) 
                    A[i] = A[i - 1];
                A[a] = B[b];
                new_len ++;
                b ++;
                if(b >= n)
                    break;
                a ++;
            }else {
                if(a_idx >= m) {
                    //copy rest B to tail of A
                    memcpy(A + a, B + b, (n-b)*sizeof(A[0]));
                    break;
                }
                a ++;
                a_idx ++;
            }
        }
    }