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Michael-Ho-BoseMichael-Ho-Bose
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Added new accepted solutions
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‎0015-3Sum.playground/Contents.swift‎

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// LeetCode: https://leetcode.com/problems/3sum/description/
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// Hint: Start from TwoSum, use sorting
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class Solution {
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func threeSum(_ nums: [Int]) -> [[Int]] {
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guard nums.count >= 3 else {
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return []
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}
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nums.sorted()
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var idxArr: [[Int]] = []
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var pair: [[Int]] = []
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var num1: [Int] = []
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for idx1 in 0..<nums.count {
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if num1.contains(nums[idx1]) {
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break
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}
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num1.append(nums[idx1])
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for idx2 in idx1+1..<nums.count {
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if pair.contains([nums[idx1], nums[idx2]].sorted()) {
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continue
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} else {
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pair.append([nums[idx1], nums[idx2]].sorted())
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idxArr.append([idx1, idx2])
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}
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}
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}
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var output: [[Int]] = []
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for i in 0..<nums.count {
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for pair in idxArr {
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if i == pair[0] || i == pair[1] {
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continue
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}
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if nums[i] + nums[pair[0]] + nums[pair[1]] == 0, !output.contains([nums[i], nums[pair[0]], nums[pair[1]]].sorted()) {
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output.append([nums[i], nums[pair[0]], nums[pair[1]]].sorted())
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}
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}
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}
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return output
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}
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}
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let solution = Solution()
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print("\(solution.threeSum([-1, 0, 1, 2, -1, -4]))")
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print("---------------------------------")
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/**
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The solution set is:
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[
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[-1, 0, 1],
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[-1, -1, 2]
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]
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*/
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print("\(solution.threeSum([-1,0,1,0]))")
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print("---------------------------------")
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/**
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The solution set is:
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[
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[-1, 0, 1]
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]
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*/
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print("\(solution.threeSum([3,0,-2,-1,1,2]))")
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print("---------------------------------")
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/**
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The solution set is:
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[
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[-2, -1, 3],
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[-2, 0, 2],
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[-1, 0, 1]
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]
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*/
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let longArray1 = [-2,10,-14,11,5,-4,2,0,-10,-10,5,7,-11,10,-2,-5,2,12,-5,14,-11,-15,-5,12,0,13,8,7,10,6,-9,-15,1,14,11,-9,-13,-10,6,-8,-5,-11,6,-9,14,11,-7,-6,8,3,-7,5,-5,3,2,10,-6,-12,3,11,1,1,12,10,-8,0,8,-5,6,-8,-6,8,-12,-14,7,9,12,-15,-12,-2,-4,-4,-12,6,7,-3,-6,-14,-8,4,4,9,-10,-7,-4,-3,1,11,-1,-8,-12,9,7,-9,10,-1,-14,-1,-8,11,12,-5,-7]
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print(longArray1.count)
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print("\(solution.threeSum(longArray1))") // Test time limit
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print("---------------------------------")
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let longArray2 = [12,-14,-5,12,-2,9,0,9,-3,-3,-14,-6,-4,13,-11,-8,0,5,-7,-6,-10,-13,-7,-14,-3,0,12,5,-8,7,3,-11,0,6,9,13,-8,-6,7,4,6,0,13,-13,-1,9,-13,6,-1,-13,-15,-4,-11,-15,-11,-7,1,-14,13,8,0,2,4,-15,-15,-2,5,-8,7,-11,11,-10,4,1,-15,10,-5,-13,2,1,11,-6,4,-15,-5,8,-7,3,1,-9,-4,-14,0,-15,8,0,-1,-2,7,13,2,-5,11,13,11,11]
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print(longArray2.count)
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print("\(solution.threeSum(longArray2))") // Test time limit
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print("---------------------------------")
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print("\(solution.threeSum([-2,0,1,1,2]))")
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/**
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The solution set is:
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[
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[-2,0,2],
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[-2,1,1]
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]
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*/

‎0015-3Sum.playground/contents.xcplayground‎

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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='5.0' target-platform='macos'>
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<timeline fileName='timeline.xctimeline'/>
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</playground>

‎0016-3SumClosest.playground/Contents.swift‎

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// LeetCode: https://leetcode.com/problems/3sum-closest/description/
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// Simple math
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class Solution {
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func threeSumClosest(_ nums: [Int], _ target: Int) -> Int {
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var sortedN = nums.sorted()
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var pairs: [Int: [Int]] = [:]
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var i = 0
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while i < sortedN.count {
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var k = i + 1
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while k < sortedN.count {
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let comp = target - sortedN[k] - sortedN[i]
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if nil == pairs[comp] {
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pairs[comp] = [i, k]
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}
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k += 1
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}
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i += 1
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}
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var output: Int?
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var third = 0
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while third < sortedN.count {
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for pair in pairs {
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if !pair.value.contains(third) {
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if pair.key == sortedN[third] {
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return target
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} else {
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if nil == output {
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output = target - pair.key + sortedN[third]
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} else if abs(pair.key - sortedN[third]) < abs(target - output!) {
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output = target - pair.key + sortedN[third]
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}
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}
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}
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}
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third += 1
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}
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return output!
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}
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}
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let solution = Solution()
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print("\(solution.threeSumClosest([-1, 2, 1, -4], 1))") // 2
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print("\(solution.threeSumClosest([-3,-2,-5,3,-4], -1))") // -2

‎0016-3SumClosest.playground/contents.xcplayground‎

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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='5.0' target-platform='macos'>
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<timeline fileName='timeline.xctimeline'/>
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</playground>

‎0019-RemoveNthNodeFromEndofList.playground/Contents.swift‎

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// LeetCode: https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/
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public class ListNode {
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public var val: Int
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public var next: ListNode?
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public init(_ val: Int, _ next: ListNode?) {
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self.val = val
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self.next = next
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}
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}
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class Solution {
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func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
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guard let head = head else {
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return nil
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}
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var arr = convertToArray(head)
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let index = arr.count - n - 1
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guard index > 0 else {
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return nil
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}
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arr[index].next = arr[index + 2]
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return head
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}
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private func convertToArray(_ head: ListNode) -> [ListNode] {
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var node: ListNode? = head
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var arr: [ListNode] = []
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while nil != node {
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arr.append(node!)
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node = node?.next
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}
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return arr
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}
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func printLinkedList(_ head: ListNode) {
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var printedStr = ""
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var currentNode: ListNode? = head
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while nil != currentNode {
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printedStr.append("\(currentNode?.val ?? -1)")
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if nil != currentNode?.next {
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printedStr.append(", ")
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}
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currentNode = currentNode?.next
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}
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print(printedStr)
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}
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}
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let solution = Solution()
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let node5 = ListNode(5, nil)
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let node4 = ListNode(4, node5)
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let node3 = ListNode(3, node4)
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let node2 = ListNode(2, node3)
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let node1 = ListNode(1, node2)
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solution.printLinkedList(node1)
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solution.removeNthFromEnd(node1, 2)
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solution.printLinkedList(node1)

‎0019-RemoveNthNodeFromEndofList.playground/contents.xcplayground‎

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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='5.0' target-platform='macos'>
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<timeline fileName='timeline.xctimeline'/>
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</playground>

‎0020-ValidParentheses.playground/Contents.swift‎

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// LeetCode: https://leetcode.com/problems/valid-parentheses/description/
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class Solution {
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func isValid(_ s: String) -> Bool {
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var arr: [Character] = []
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for c in s {
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switch c {
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case "(", "[", "{":
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arr.append(c)
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case ")":
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let char = pop(&arr)
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if nil == char || char != "(" {
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return false
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}
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case "]":
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let char = pop(&arr)
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if nil == char || char != "[" {
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return false
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}
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case "}":
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let char = pop(&arr)
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if nil == char || char != "{" {
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return false
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}
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default:
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break
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}
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}
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return arr.count == 0
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}
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private func pop(_ arr: inout [Character]) -> Character? {
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guard arr.count > 0 else {
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return nil
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}
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return arr.remove(at: arr.count-1)
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}
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}
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let solution = Solution()
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print("\(solution.isValid("()"))")
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print("\(solution.isValid("()[]{}"))")
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print("\(solution.isValid("(]"))")
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print("\(solution.isValid("([)]"))")
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print("\(solution.isValid("{[]}"))")
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print("\(solution.isValid("["))")

‎0020-ValidParentheses.playground/contents.xcplayground‎

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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='5.0' target-platform='macos'>
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<timeline fileName='timeline.xctimeline'/>
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</playground>

‎0023-MergeKSortedLists.playground/Contents.swift‎

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// LeetCode: https://leetcode.com/problems/merge-k-sorted-lists/description/
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public class ListNode {
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public var val: Int
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public var next: ListNode?
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public init(_ val: Int) {
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self.val = val
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self.next = nil
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}
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}
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class Solution {
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func mergeKLists(_ lists: [ListNode?]) -> ListNode? {
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var arr: [Int] = []
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for head in lists {
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arr = arr + toArray(head)
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}
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arr = arr.sorted()
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return toLinkedList(arr: arr)
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}
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private func toArray(_ head: ListNode?) -> [Int] {
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guard nil != head else {
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return []
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}
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var arr: [Int] = []
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var node = head
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while nil != node {
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arr.append((node?.val)!)
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node = node?.next
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}
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return arr
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}
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private func toLinkedList(arr: [Int]) -> ListNode? {
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guard arr.count > 0 else {
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return nil
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}
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guard arr.count > 1 else {
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return ListNode(arr[0])
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}
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var head = ListNode(arr[0])
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var node: ListNode? = ListNode(arr[1])
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head.next = node
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var index = 1
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while index + 1 < arr.count {
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node?.next = ListNode(arr[index+1])
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node = node?.next
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index += 1
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}
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return head
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}
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}

‎0023-MergeKSortedLists.playground/contents.xcplayground‎

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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='5.0' target-platform='ios'>
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<timeline fileName='timeline.xctimeline'/>
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</playground>

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