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 == )
             return;
         if(m == ) {
             memcpy(A, B, n * sizeof(B[]));
             return;
         }
         int a = ;
         int b = ;
         int a_idx = ;
         int new_len = m;
         while(true) {
             if(A[a] >= B[b]) {
                 //insert B[b] before A[a]
                 for(int i = new_len; i >= a + ; i --)
                     A[i] = A[i - ];
                 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[]));
                     break;
                 }
                 a ++;
                 a_idx ++;
             }
         }
     }