[Leetcode] Merge Sorted Array

Problem 

Given two sorted integer arrays A and B, merge B into A as one sorted array. 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.

Algorithm

If merge two arrays from left to right, we may find some difficulties to relocate elements in A. For example, if A = [3,4, ] B = [1]. 

1. Relocate m elements in A to range A[m-1, m+n-1], then merge two arrays from left to right. 

For example, after relocation,  A = [ ,3,4] B = [1], then merge. 

2. Merge two arrays in descending order, since array A is empty on the right side. 

Code