Note:
You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2. The number of elements initialized in nums1 and nums2 are m and n respectively.

nums1已經是m+n長度了，不用新申請空間。

從後向前復制。

 1 class Solution:
 2     def merge(self, l1, m, l2, n):
 3         """
 4         :type nums1: List[int]
 5         :type m: int
 6         :type nums2: List[int]
 7         :type n: int
 8         :rtype: void Do not return anything, modify nums1 in-place instead.
 
 9         """
10         i = m - 1
11         j = n - 1
12 
13         end = m+n-1
14         while(i >= 0 and j >= 0):
15             if(l1[i] > l2[j]):
16                 l1[end] = l1[i]
17                 i-=1
18             else:
19                 l1[end] = l2[j]
20                 j -= 1
21
 
             end -=1
22 
23         while (j>=0):
24             l1[end] = l2[j]
25             j -= 1
26             end-=1

88. Merge Sorted Array（從後向前復制）