Leetcode:Merge Sorted Array 归并排序

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.

class Solution {
public:
    void merge(int A[], int m, int B[], int n) {
        assert(A != NULL && B != NULL && m >= 0 && n >= 0);
        int ia = m - 1;
        int ib = n - 1;
        int idx = m + n - 1;
        while (ia >= 0 && ib >= 0) {
            if (A[ia] >= B[ib]) {
                A[idx--] = A[ia--];
            } else {
                A[idx--] = B[ib--];
            }
        }
        while (ia >= 0) {
            A[idx--] = A[ia--];
        }
        while (ib >= 0) {
            A[idx--] = B[ib--];
        }
    }
};