Contents.swift

/**
 You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively.

 Merge nums1 and nums2 into a single array sorted in non-decreasing order.

 The final sorted array should not be returned by the function, but instead be stored inside the array nums1. To accommodate this, nums1 has a length of m + n, where the first m elements denote the elements that should be merged, and the last n elements are set to 0 and should be ignored. nums2 has a length of n.

  

 Example 1:
 Input: nums1 = [1,2,3,0,0,0], m = 3, nums2 = [2,5,6], n = 3
 Output: [1,2,2,3,5,6]
 Explanation: The arrays we are merging are [1,2,3] and [2,5,6].
 The result of the merge is [1,2,2,3,5,6] with the underlined elements coming from nums1.
 
 Example 2:
 Input: nums1 = [1], m = 1, nums2 = [], n = 0
 Output: [1]
 Explanation: The arrays we are merging are [1] and [].
 The result of the merge is [1].
 
 Example 3:
 Input: nums1 = [0], m = 0, nums2 = [1], n = 1
 Output: [1]
 Explanation: The arrays we are merging are [] and [1].
 The result of the merge is [1].
 Note that because m = 0, there are no elements in nums1. The 0 is only there to ensure the merge result can fit in nums1.
  

 Constraints:
 - nums1.length == m + n
 - nums2.length == n
 - 0 <= m, n <= 200
 - 1 <= m + n <= 200
 - -109 <= nums1[i], nums2[j] <= 109
  

 Follow up: Can you come up with an algorithm that runs in O(m + n) time?
 */
class Solution {
    func merge(_ nums1: inout [Int], _ m: Int, _ nums2: [Int], _ n: Int) -> [Int] {
        guard !nums1.isEmpty else {
            nums1 = nums2
            return nums1
        }
        guard !nums2.isEmpty else { return Array(nums1.prefix(m)) }
        nums1 = Array(nums1.prefix(m)) + nums2
        // Insert order
        var preIndex: Int = 0
        var current: Int = 1
        for i in 1..<(m + n) {
            preIndex = i - 1
            current = nums1[i]
            while preIndex >= 0 && nums1[preIndex] > current {
                nums1[preIndex + 1] = nums1[preIndex]
                preIndex -= 1
            }
            nums1[preIndex + 1] = current
        }
        return nums1
    }
}