NigelJu

class Solution {
    func maximumProduct(_ nums: [Int]) -> Int {
        if nums.count == 3 {
            return nums.reduce(1, *)
        }
        
        let sortedNums = nums.sorted(by: >)
        let allMaxNum = sortedNums[0] * sortedNums[1] * sortedNums[2]
        let minMixedMaxNum = sortedNums.first! * sortedNums[nums.count - 2] * sortedNums.last!   
        return max(allMaxNum, minMixedMaxNum)

NigelJu

class Solution {
    func canPlaceFlowers(_ flowerbed: [Int], _ n: Int) -> Bool {
        
        if n == 0 { return true }
        
        if flowerbed.count == 1 {
            return n == 1 && flowerbed.first! == 0
        }
        
        var flowerCount = n

NigelJu

class Solution {
    func intersection(_ nums1: [Int], _ nums2: [Int]) -> [Int] {
        var mapping = [Int: Int]()
        var results = [Int]()
        nums1.forEach( { mapping.updateValue(0, forKey: $0) } )
        for n2 in nums2 {
            if let _ = mapping[n2] {
                mapping.removeValue(forKey: n2)
                results.append(n2)
            }

NigelJu

class Solution {
    func intersection(_ nums1: [Int], _ nums2: [Int]) -> [Int] {
       let set1 = Set(nums1)
        let set2 = Set(nums2)
        return Array(set1.intersection(set2))
    }
}

NigelJu

class Solution {
    func isSameTree(_ p: TreeNode?, _ q: TreeNode?) -> Bool {
        if p == nil && q == nil { return true }
        guard let tree1 = p, let tree2 = q, tree1.val == tree2.val else { return false }
        return isSameTree(tree1.left, tree2.left) && isSameTree(tree1.right, tree2.right)
    }
}

NigelJu

class Solution {
    func convertToTitle(_ n: Int) -> String {
        
        var num = n
        var intToStr = [Int: String]()
        var result = ""
    
        intToStr.updateValue("Z", forKey: 0)
        for index in 1 ... 25 {
            let char = String(UnicodeScalar(64 + index)!)

NigelJu

class Solution {
    func convertToTitle(_ n: Int) -> String {
        
        var num = n
        var intToStr = [Int: String]()
        var result = ""
    
        intToStr.updateValue("Z", forKey: 0)
        for index in 1 ... 25 {
            let char = String(UnicodeScalar(64 + index)!)

NigelJu

class Solution {
    func maxDepth(_ root: TreeNode?) -> Int {
        guard let root = root else { return 0 }
        
        var maxLeftDepth = 1
        var maxRightDepth = 1
        
        maxLeftDepth += maxDepth(root.left)
        maxRightDepth += maxDepth(root.right)
        

NigelJu

class Solution {
    func maxDepth(_ root: TreeNode?) -> Int {
        guard let root = root else { return 0 }
        
        var maxLeftDepth = 1
        var maxRightDepth = 1
        
        if let leftNood = root.left {
            maxLeftDepth += maxDepth(leftNood)
        }

NigelJu

class Solution {
    func majorityElement(_ nums: [Int]) -> Int {
        return nums.sorted(by: >)[nums.count / 2]
    }
}