Create Merge Sorted Array 

后插法，从A的尾部进行插入，当然A的空间为n+m，所以说不用担心A的数据被覆盖的情况，注意当有一方的数据没了而另一个数组还有数据的时候注意处理方式。

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.