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merge-sort.swift
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merge-sort.swift
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class Solution {
func sortArray(_ nums: [Int]) -> [Int] {
return topDownMergeSort(nums)
}
private func topDownMergeSort(_ nums: [Int]) -> [Int] {
guard nums.count > 1 else { return nums }
let mid = nums.count / 2
let sortedLeft = topDownMergeSort(Array(nums[0..<mid]))
let sortedRight = topDownMergeSort(Array(nums[mid..<nums.count]))
return merge(sortedLeft, sortedRight)
}
private func merge(_ first: [Int], _ second: [Int]) -> [Int] {
var result = [Int]()
var i = 0
var j = 0
while i < first.count && j < second.count {
let firstNum = first[i]
let secondNum = second[j]
if firstNum < secondNum {
result.append(firstNum)
i += 1
} else {
result.append(secondNum)
j += 1
}
}
if !first.isEmpty {
while i < first.count {
result.append(first[i])
i += 1
}
}
if !second.isEmpty {
while j < second.count {
result.append(second[j])
j += 1
}
}
return result
}
}