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Commit 06e46ff

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Day 92
1 parent 30e967d commit 06e46ff

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import UIKit
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/*
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Two elements of a binary search tree (BST) are swapped by mistake.
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Recover the tree without changing its structure.
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Example 1:
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Input: [1,3,null,null,2]
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1
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/
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3
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\
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2
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Output: [3,1,null,null,2]
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3
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/
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1
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\
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2
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Example 2:
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Input: [3,1,4,null,null,2]
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3
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/ \
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1 4
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/
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2
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Output: [2,1,4,null,null,3]
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2
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/ \
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1 4
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/
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3
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Follow up:
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A solution using O(n) space is pretty straight forward.
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Could you devise a constant space solution?
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*/
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/**
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* Definition for a binary tree node.
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*/
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public class TreeNode {
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public var val: Int
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public var left: TreeNode?
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public var right: TreeNode?
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public init() { self.val = 0; self.left = nil; self.right = nil; }
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public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
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public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
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self.val = val
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self.left = left
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self.right = right
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}
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}
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class Solution {
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var first: TreeNode?
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var second: TreeNode?
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var prev = TreeNode(Int.min)
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func recoverTree(_ root: TreeNode?) {
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inOrder(root)
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let temp = first!.val
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first!.val = second!.val
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second!.val = temp
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}
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func inOrder(_ node: TreeNode?) {
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guard let node = node else {return}
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inOrder(node.left)
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if first == nil && prev.val >= node.val {
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first = prev
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}
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if first != nil && prev.val >= node.val {
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second = node
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}
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prev = node
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inOrder(node.right)
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}
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}
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import Foundation
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import XCTest
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class SolutionTests: XCTestCase {
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var solution: Solution!
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override func setUp() {
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super.setUp()
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solution = Solution()
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}
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func test1() {
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// let results = solution.threeSum([-1, 1])
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// XCTAssertEqual(results, [])
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}
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}
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SolutionTests.defaultTestSuite.run()
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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>

‎99. Recover Binary Search Tree.playground/playground.xcworkspace/contents.xcworkspacedata‎

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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
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<plist version="1.0">
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<dict>
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<key>IDEDidComputeMac32BitWarning</key>
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<true/>
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</dict>
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</plist>
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<?xml version="1.0" encoding="UTF-8"?>
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<Timeline
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version = "3.0">
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<TimelineItems>
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<LoggerValueHistoryTimelineItem
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documentLocation = "file:///Users/zenglekidd/Desktop/99.%20Recover%20Binary%20Search%20Tree.playground#CharacterRangeLen=1086&amp;CharacterRangeLoc=509&amp;EndingColumnNumber=1&amp;EndingLineNumber=91&amp;StartingColumnNumber=0&amp;StartingLineNumber=47&amp;Timestamp=624204658.73497"
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selectedRepresentationIndex = "0"
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shouldTrackSuperviewWidth = "NO">
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</LoggerValueHistoryTimelineItem>
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</TimelineItems>
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</Timeline>

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