voxqhuy

class ViewController: UIViewController {

    @IBOutlet weak var textField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.


        let datePicker = UIDatePicker()

voxqhuy

// 1 3 800
// 1 2 500
// 2 3 500
// 1 70
// 2 40
// 1 3
public static class Station {
  int city;
  int price;
  int capacity;

voxqhuy

// https://leetcode.com/problems/add-and-search-word-data-structure-design/
// For add():
// Time: O(n), Space: O(n)

// For search():
// Time: O(n), Space: O(n) because of the recursive calls
// Where there are wildcards:
// The absolute worst case we can have 26 children at each node, traversing through all nodes with DFS will take 26^n (n nodes, each nodes have 26 children/characters). 26^n is technically 2^n. Therefore,
// Time: O(2^n), Space: O(n) because we only have at max n calls on the stack at any given time.
// or O(m) where m is the total number of characters on the trie.

voxqhuy

// https://leetcode.com/problems/maximum-depth-of-binary-tree/
// Recursive
// Time: O(n), Space: O(n)
func maxDepth(_ root: TreeNode?) -> Int {
    guard let root = root else { return 0 }
    return 1 + max(maxDepth(root.left), maxDepth(root.right))
}

// Iterative
// Time: O(n), Space: O(n)

voxqhuy

// https://leetcode.com/problems/subsets/
// Approach 1: Cascading
// Time: O(n*2^n), Space: O(n*2^n)
func subsets(_ nums: [Int]) -> [[Int]] {
    var result = [[Int]]()
    result.append([])
    for num in nums {
        for currSet in result {
            result.append(currSet + [num])
        }

voxqhuy

// https://leetcode.com/problems/binary-tree-maximum-path-sum/
// O(n), Space O(n)
var globalMax = Int.min
func maxPathSum(_ root: TreeNode?) -> Int {
    maxPath(root)
    return globalMax
}

func maxPath(_ root: TreeNode?) -> Int {
    guard let root = root else { return 0 }

voxqhuy

// ------------------MEDIUM------------------ //
// https://leetcode.com/problems/clone-graph/
// DFS
// Time: O(n), Space: O(n)
func cloneGraph(_ node: Node?) -> Node? {
    var dict = [Int : Node]()

    return cloneNode(node, &dict)
}

voxqhuy

// https://leetcode.com/problems/top-k-frequent-elements/
// O(n), O(n)
func topKFrequent(_ nums: [Int], _ k: Int) -> [Int] {
      var freqDict = [Int : Int]()
      var bucket = [Int : [Int]]()
      var result = [Int]()
      var topFreq = 0

      // O(n)
      for num in nums {

voxqhuy

// https://leetcode.com/problems/number-of-islands/
// Time: n*m, Space 1
func numIslands(_ grid: [[Character]]) -> Int {
    var gridCopy = grid
    var islandCount = 0

    for i in 0..<gridCopy.count {
        for j in 0..<gridCopy[0].count {
            if gridCopy[i][j] != "0" {
                markAdjacentLands(i, j, inGrid: &gridCopy)

voxqhuy

// Toaster
class Bread {
	var cookedTime: Double = 0.0
}

enum TrayLevel { 
	case down 
	case up 
}