LeetCode: 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 andn respectively.

   void merge(int A[], int m, int B[], int n) {  
     int j = m+n-1, i = m-1,k;  
     if(n <= 0)return;  
     if(m<=0)  
     {  
       int k = 0;  
       while(k<n)  
       {  
         A[k] = B[k];  
         k++;  
       }  
       return;  
     }  
     while(i>=0)  
     {  
       A[j] = A[i];  
       i--;  
       j--;  
     }  
     i = j+1; j = 0, k = 0;  
     while(i<m+n && j<n)  
     {  
       if(A[i] <= B[j])  
       {  
         A[k++] = A[i++];  
       }  
       else A[k++] = B[j++];  
     }  
     while(j<n)  
     {  
       A[k++] = B[j++];  
     }  
   }