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  • [Swift]LeetCode993. 二叉树的堂兄弟节点 | Cousins in Binary Tree

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    ➤微信公众号:山青咏芝(shanqingyongzhi)
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    ➤原文地址:https://www.cnblogs.com/strengthen/p/10390643.html 
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    In a binary tree, the root node is at depth 0, and children of each depth k node are at depth k+1.

    Two nodes of a binary tree are cousins if they have the same depth, but have different parents.

    We are given the root of a binary tree with unique values, and the values x and y of two different nodes in the tree.

    Return true if and only if the nodes corresponding to the values x and y are cousins. 

    Example 1:

    Input: root = [1,2,3,4], x = 4, y = 3
    Output: false
    

    Example 2:

    Input: root = [1,2,3,null,4,null,5], x = 5, y = 4
    Output: true
    

    Example 3:

    Input: root = [1,2,3,null,4], x = 2, y = 3
    Output: false

    Note:

    1. The number of nodes in the tree will be between 2 and 100.
    2. Each node has a unique integer value from 1 to 100.

    在二叉树中,根节点位于深度 0 处,每个深度为 k 的节点的子节点位于深度 k+1 处。

    如果二叉树的两个节点深度相同,但父节点不同,则它们是一对堂兄弟节点

    我们给出了具有唯一值的二叉树的根节点 root,以及树中两个不同节点的值 x 和 y

    只有与值 x 和 y 对应的节点是堂兄弟节点时,才返回 true。否则,返回 false。 

    示例 1:

    输入:root = [1,2,3,4], x = 4, y = 3
    输出:false
    

    示例 2:

    输入:root = [1,2,3,null,4,null,5], x = 5, y = 4
    输出:true
    

    示例 3:

    输入:root = [1,2,3,null,4], x = 2, y = 3
    输出:false 

    提示:

    1. 二叉树的节点数介于 2 到 100 之间。
    2. 每个节点的值都是唯一的、范围为 1 到 100 的整数。

    Runtime: 12 ms

    Memory Usage: 18.4 MB
     1 /**
     2  * Definition for a binary tree node.
     3  * public class TreeNode {
     4  *     public var val: Int
     5  *     public var left: TreeNode?
     6  *     public var right: TreeNode?
     7  *     public init(_ val: Int) {
     8  *         self.val = val
     9  *         self.left = nil
    10  *         self.right = nil
    11  *     }
    12  * }
    13  */
    14 class Solution {
    15     var ddd:Int = 0
    16     func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
    17         var px:TreeNode? = dfs(root, nil, x, 0, 1)
    18         var py:TreeNode? = dfs(root, nil, y, 0, -1)
    19         return x != y && px != nil && py != nil && px!.val != py!.val && ddd == 0       
    20     }
    21     
    22     func dfs(_ cur:TreeNode?,_ par:TreeNode?,_ x:Int,_ dep:Int,_ mul:Int) -> TreeNode?
    23     {
    24         if cur == nil {return nil}
    25         if cur!.val == x
    26         {
    27             ddd += dep * mul
    28             return par
    29         }
    30         var res:TreeNode? = dfs(cur!.left, cur, x, dep + 1, mul)
    31         if res != nil {return res}
    32         res = dfs(cur!.right, cur, x, dep+1, mul)
    33         return res        
    34     }
    35 }

     1 /**
     2  * Definition for a binary tree node.
     3  * public class TreeNode {
     4  *     public var val: Int
     5  *     public var left: TreeNode?
     6  *     public var right: TreeNode?
     7  *     public init(_ val: Int) {
     8  *         self.val = val
     9  *         self.left = nil
    10  *         self.right = nil
    11  *     }
    12  * }
    13  */
    14 class Solution {
    15     func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
    16         guard let root = root else {
    17             return false
    18         }
    19         
    20         var rootVal = -1
    21         var cousinLevel = -1
    22         var isCousins = false
    23         
    24         func goNext(_ node: TreeNode?, _ level: Int, _ parent: TreeNode) {
    25             guard let node = node else {
    26                 return
    27             }
    28             
    29             if node.val == x || node.val == y {
    30                 if rootVal == -1 {
    31                     rootVal = parent.val
    32                     cousinLevel = level
    33                 } else if rootVal != parent.val && cousinLevel == level {
    34                     isCousins = true
    35                 }
    36             }
    37             
    38             goNext(node.left, level + 1, node)
    39             goNext(node.right, level + 1, node)
    40         }
    41         
    42         goNext(root.left, 1, root)
    43         goNext(root.right, 1, root)
    44         
    45         return isCousins
    46     }
    47 }

     1 /**
     2  * Definition for a binary tree node.
     3  * public class TreeNode {
     4  *     public var val: Int
     5  *     public var left: TreeNode?
     6  *     public var right: TreeNode?
     7  *     public init(_ val: Int) {
     8  *         self.val = val
     9  *         self.left = nil
    10  *         self.right = nil
    11  *     }
    12  * }
    13  */
    14 class Solution {
    15     func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
    16         var queue = [TreeNode]()
    17         guard let root = root else {
    18             return false
    19         }
    20         
    21         queue.append(root)
    22         while queue.count > 0 {
    23             let size = queue.count 
    24             var level = [Int]()
    25             for i in 0..<size {
    26                 let temp = queue.removeFirst()
    27                 if let left = temp.left, let right = temp.right {
    28                     if (left.val == x && right.val == y) || (left.val == y && right.val == x) {
    29                         return false
    30                     }
    31                     queue.append(left)
    32                     queue.append(right)
    33                     level.append(left.val)
    34                     level.append(right.val)
    35                 } else if let left = temp.left {
    36                     queue.append(left)
    37                     level.append(left.val)
    38                 } else if let right = temp.right{
    39                     queue.append(right)
    40                     level.append(right.val)
    41                 }
    42             }
    43             if level.contains(x) && level.contains(y) {
    44                 return true
    45             }
    46         }
    47         return false
    48     }
    49 }

     1 /**
     2  * Definition for a binary tree node.
     3  * public class TreeNode {
     4  *     public var val: Int
     5  *     public var left: TreeNode?
     6  *     public var right: TreeNode?
     7  *     public init(_ val: Int) {
     8  *         self.val = val
     9  *         self.left = nil
    10  *         self.right = nil
    11  *     }
    12  * }
    13  */
    14 class Solution {
    15     func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
    16         var depths = [Int:Int]()
    17         var parents = [Int:TreeNode]()
    18         find(root, val: x, depths: &depths, parents: &parents)
    19         find(root, val: y, depths: &depths, parents: &parents)
    20         if let xDepth = depths[x], let yDepth = depths[y], let xParent = parents[x], let yParent = parents[y] {
    21             return xDepth == yDepth && xParent !== yParent
    22         }
    23         return false
    24     }
    25     
    26     func find(_ node: TreeNode?, val: Int, depth: Int = 0, depths: inout [Int:Int], parents: inout [Int:TreeNode]) {
    27         guard let node = node else {
    28             return
    29         }
    30         if let left = node.left, left.val == val {
    31             parents[val] = node
    32             depths[val] = depth
    33             return
    34         }
    35         else if let right = node.right, right.val == val {
    36             parents[val] = node 
    37             depths[val] = depth
    38             return
    39         }
    40         find(node.left, val: val, depth: depth + 1, depths: &depths, parents: &parents)
    41         find(node.right, val: val, depth: depth + 1, depths: &depths, parents: &parents)
    42     }
    43 }

     1 class Solution {
     2   private var xVal: Int!
     3   private var yVal: Int!
     4 
     5   private var xPair: (lvl: Int, prnt: Int)?
     6   private var yPair: (lvl: Int, prnt: Int)?
     7 
     8   func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
     9     xVal = x
    10     yVal = y
    11     search(lvl: 0, prevVal: 0, node: root)
    12     return xPair?.lvl == yPair?.lvl && xPair?.prnt != yPair?.prnt
    13   }
    14   
    15   private func search(lvl: Int, prevVal: Int, node: TreeNode?) {
    16     guard let n = node else { return }
    17     if n.val == xVal! {
    18       xPair = (lvl, prevVal)
    19     } else if n.val == yVal! {
    20       yPair = (lvl, prevVal)
    21     }
    22     search(lvl: lvl + 1, prevVal: n.val, node: n.left)
    23     search(lvl: lvl + 1, prevVal: n.val, node: n.right)
    24   }
    25 }

     1 /**
     2  * Definition for a binary tree node.
     3  * public class TreeNode {
     4  *     public var val: Int
     5  *     public var left: TreeNode?
     6  *     public var right: TreeNode?
     7  *     public init(_ val: Int) {
     8  *         self.val = val
     9  *         self.left = nil
    10  *         self.right = nil
    11  *     }
    12  * }
    13  */
    14 class Solution {
    15     
    16     func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
    17         let (foundX, foundY, depth) = isCousins(root, 0, x, y)
    18         return foundX && foundY && depth != nil
    19     }
    20 
    21     func isCousins(_ root: TreeNode?, _ depth: Int, _ x: Int, _ y: Int) -> (foundX: Bool, foundY: Bool, depth: Int?) {
    22         guard let root = root else {
    23             return (false, false, nil)
    24         }
    25 
    26         if root.val == x {
    27             return (true, false, depth)
    28         } else if root.val == y {
    29             return (false, true, depth)
    30         }
    31 
    32         var xDepth: Int? = nil
    33         var yDepth: Int? = nil
    34 
    35         let (leftFoundX, leftFoundY, leftDepth) = isCousins(root.left, depth + 1, x, y)
    36 
    37         if leftFoundX && leftFoundY {
    38             return (leftFoundX, leftFoundY, leftDepth)
    39         }
    40 
    41         xDepth = (leftFoundX) ? leftDepth : xDepth
    42         yDepth = (leftFoundY) ? leftDepth : yDepth
    43 
    44         let (rightFoundX, rightFoundY, rightDepth) = isCousins(root.right, depth + 1, x, y)
    45 
    46         if rightFoundX && rightFoundY {
    47             return (rightFoundX, rightFoundY, rightDepth)
    48         }
    49 
    50         xDepth = (rightFoundX) ? rightDepth : xDepth
    51         yDepth = (rightFoundY) ? rightDepth : yDepth
    52 
    53         let foundX = leftFoundX || rightFoundX
    54         let foundY = leftFoundY || rightFoundY
    55         if foundX && foundY {
    56             if xDepth == yDepth && (xDepth != (depth+1)) {
    57                 return (true, true, xDepth)
    58             } else {
    59                 return (true, true, nil)
    60             }
    61         } else {
    62             return (foundX, foundY, xDepth ?? yDepth)
    63         }
    64     }    
    65 }

      1 /**
      2  * Definition for a binary tree node.
      3  * public class TreeNode {
      4  *     public var val: Int
      5  *     public var left: TreeNode?
      6  *     public var right: TreeNode?
      7  *     public init(_ val: Int) {
      8  *         self.val = val
      9  *         self.left = nil
     10  *         self.right = nil
     11  *     }
     12  * }
     13  */
     14 protocol Queue {
     15     associatedtype T
     16     var count: Int { get }
     17     var isEmpty: Bool { get }
     18     var top: T? { get }
     19     func enqueue(_ item: T)
     20     func dequeue() -> T?
     21 }
     22 
     23 class LinkedListNode<T> {
     24     var value: T
     25     var next: LinkedListNode<T>?
     26     init(_ value: T) {
     27         self.value = value
     28     }
     29     init(_ value: T, _ next: LinkedListNode<T>) {
     30         self.value = value
     31         self.next = next
     32     }
     33 }
     34 
     35 class LinkedQueue<Type> : Queue {
     36     typealias T = Type
     37     private var head: LinkedListNode<T>?
     38     private var tail: LinkedListNode<T>?
     39     private(set) var count: Int = 0
     40     var isEmpty: Bool {
     41         return head == nil
     42     }
     43     var top: T? {
     44         return head?.value
     45     }
     46     
     47     init () {
     48         self.head = nil
     49         self.tail = nil
     50     }
     51     init(_ initialValue: T) {
     52         self.head = LinkedListNode<T>(initialValue)
     53         self.tail = self.head
     54     }
     55     
     56     func enqueue(_ item: T) {
     57         if isEmpty {
     58             self.tail = LinkedListNode<T>(item)
     59             self.head = self.tail
     60         } else {
     61             self.tail!.next = LinkedListNode<T>(item)
     62             self.tail = self.tail!.next
     63         }
     64         count += 1
     65     }
     66     
     67     func dequeue() -> Type? {
     68         if let validHead = self.head {
     69             let data = validHead.value
     70             self.head = validHead.next
     71             count -= 1
     72             return data
     73         } else {
     74             return nil
     75         }
     76     }
     77 }
     78 
     79 
     80 class Solution {
     81     func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
     82         var xParent: Int? = nil
     83         var yParent: Int? = nil
     84         var xDepth: Int? = nil
     85         var yDepth: Int? = nil
     86         
     87         typealias Level = Int
     88         let frontier = LinkedQueue<(TreeNode, Level, TreeNode?)>()
     89         frontier.enqueue((root!, 0, nil))
     90         
     91         while true {
     92             guard let (node, level, parent) = frontier.dequeue() else {
     93                 break
     94             }
     95             if node.val == x {
     96                 xParent = parent?.val
     97                 xDepth = level
     98             }
     99             if node.val == y {
    100                 yParent = parent?.val
    101                 yDepth = level
    102             }
    103             if let leftChild = node.left {
    104                 frontier.enqueue((leftChild, level + 1, node))
    105             }
    106             
    107             if let rightChild = node.right {
    108                 frontier.enqueue((rightChild, level + 1, node))
    109             }
    110         }
    111         
    112         return (xDepth != nil) && (yDepth != nil) && (xDepth == yDepth) && (xParent != yParent)
    113     }
    114 }

     1 /**
     2  * Definition for a binary tree node.
     3  * public class TreeNode {
     4  *     public var val: Int
     5  *     public var left: TreeNode?
     6  *     public var right: TreeNode?
     7  *     public init(_ val: Int) {
     8  *         self.val = val
     9  *         self.left = nil
    10  *         self.right = nil
    11  *     }
    12  * }
    13  */
    14 class Solution {
    15     var xParent = -1
    16     var yParent = -1
    17     var xDepth = Int.min
    18     var yDepth = Int.max
    19     
    20     func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
    21         if let r = root {
    22             countDepth(r, r.left, x, y, 1)
    23             countDepth(r, r.right, x, y, 1)
    24             if xParent != yParent && xDepth == yDepth {
    25                 return true
    26             }
    27         } 
    28         return false
    29     }
    30     
    31     func countDepth(_ parent: TreeNode, _ node: TreeNode?, _ x: Int, _ y: Int, _ depth: Int) {
    32         if let r = node {
    33             if r.val == x {
    34                 xParent = parent.val
    35                 xDepth = depth
    36             }   
    37             
    38             if r.val == y {
    39                 yParent = parent.val
    40                 yDepth = depth
    41             }
    42             
    43             countDepth(r, r.left, x, y, depth+1)
    44             countDepth(r, r.right, x, y, depth+1)
    45         }
    46     }
    47 }

     1 /**
     2  * Definition for a binary tree node.
     3  * public class TreeNode {
     4  *     public var val: Int
     5  *     public var left: TreeNode?
     6  *     public var right: TreeNode?
     7  *     public init(_ val: Int) {
     8  *         self.val = val
     9  *         self.left = nil
    10  *         self.right = nil
    11  *     }
    12  * }
    13  */
    14 class Solution {
    15     var xNode: (Int, TreeNode?)?
    16     var yNode: (Int, TreeNode?)?
    17     func isCousins(_ root: TreeNode?, _ x: Int, _ y: Int) -> Bool {
    18         helper(root, nil, x, y, 0)
    19         guard let xNode = xNode, let yNode = yNode else { return false }
    20         return xNode.0 == yNode.0 && xNode.1 !== yNode.1
    21     }
    22     
    23     private func helper(_ root: TreeNode?, _ parent: TreeNode?, _ x: Int, _ y: Int, _ depth: Int) {
    24         guard let root = root else { return }
    25         if root.val == x {
    26             xNode = (depth, parent)
    27         }
    28         if root.val == y {
    29             yNode = (depth, parent)
    30         }
    31         helper(root.left, root, x, y, depth + 1)
    32         helper(root.right, root, x, y, depth + 1)
    33     }
    34 }
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  • 原文地址:https://www.cnblogs.com/strengthen/p/10390643.html
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