derekli66

private class ListNode {
    var next: ListNode?
    var prev: ListNode?
    var key: Int = 0
}

class Stack {
    private var head: ListNode?
    private var tail: ListNode?
    private var count: Int = 0

derekli66

private class ListNode {
    var next: ListNode?
    var prev: ListNode?
    var key: Int = 0
}
/*
 push to back, peek/pop from front, size and is empty
 */
class Queue {
    private var head: ListNode?

derekli66

class Solution {
    func addBinary(_ a: String, _ b: String) -> String {
        var result = ""
        
        let aStrArr = Array(String(a.reversed())).map{ String($0) }
        let bStrArr = Array(String(b.reversed())).map{ String($0) }
        
        var index = 0
        var advanced = 0
        while index < aStrArr.count && index < bStrArr.count {

derekli66

class MaxHeap {
    private var array = Array<Int>()
    
    func leftChild(_ i:Int) -> Int {
        return 2*i+1
    }
    
    func rightChild(_ i:Int) -> Int {
        return 2*i+2

derekli66

import typing
from typing import List 
import sys


class Solution:
    def __init__(self) -> None:
        self.amount_memorization = {}
    
    def coinChange(self, coins: List[int], amount: int) -> int:

derekli66

import UIKit

var arr = [Int?]()
arr.append(nil)

func parent(_ i: Int) -> Int {
    return i/2
}

derekli66

import Foundation

func knapsack(_ weights: Array<Int>,_ values: Array<Int>,_ index: Int,_ remainingWeight: Int,_ cache: inout Array<Array<Int>>) -> Int {
    
    if (index < 0) { return 0 }
    
    if (cache[index][remainingWeight] != -1) {
        return cache[index][remainingWeight]
    }
    

derekli66

import Foundation

func knapsack(_ weights: Array<Int>,_ values: Array<Int>,_ index: Int,_ remainingWeight: Int) -> Int {
    
    if (index < 0) { return 0 }
    
    var choosedValue: Int = 0
    if (remainingWeight >= weights[index]) {
        // Choose
        choosedValue = values[index] + knapsack(weights, values, index - 1, remainingWeight - weights[index])

derekli66

import Foundation

//-------------Basic BST Operation-------------------
class Node
{
  var key: Int?
  var left: Node?
  var right: Node?
  
  var description: String {

derekli66

import Foundation

//-------------Basic BST Operation-------------------
class Node
{
  var key: Int?
  var left: Node?
  var right: Node?
  var parent: Node?