[Leetcode] 88. Merge Sorted Arra

原题如下：
Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.

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.

大意是：
给定两个有序数组nums1和nums2，合并nums2到nums1中，并使得nums1为有序数组

注意：
你可以认为nums1有足够的空间(size >= m + n)；

使用末尾填充法

从后往前填充即可，当nums2结束了，nums1数组后面的都是有序的；

复杂度

时间复杂度 O(n + m)
空间复杂度 O(1)

代码实现如下：

func merge(_ nums1: inout [Int], _ m: Int, _ nums2: [Int], _ n: Int) {
    var i = m - 1
    var j = n - 1
    var tar = m + n - 1
    
    while j > 0 {
        if i >= 0 && nums1[i] > nums2[j] {
            nums1[tar] = nums1[i]
            i = i - 1
        } else {
            nums1[tar] = nums2[j]
            j = j - 1
        }
        
        tar = tar - 1
    }
}