[Swift]LeetCode897. 递增顺序查找树 | Increasing Order Search 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/10606692.html 
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Given a tree, rearrange the tree in in-order so that the leftmost node in the tree is now the root of the tree, and every node has no left child and only 1 right child.

Example 1:
Input: [5,3,6,2,4,null,8,1,null,null,null,7,9]

       5
      / 
    3    6
   /     
  2   4    8
 /        /  
1        7   9

Output: [1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]

 1
  
   2
    
     3
      
       4
        
         5
          
           6
            
             7
              
               8
                
                 9  

Note:

1. The number of nodes in the given tree will be between 1 and 100.
2. Each node will have a unique integer value from 0 to 1000.

---

给定一个树，按中序遍历重新排列树，使树中最左边的结点现在是树的根，并且每个结点没有左子结点，只有一个右子结点。 

示例 ：

输入：[5,3,6,2,4,null,8,1,null,null,null,7,9]

       5
      / 
    3    6
   /     
  2   4    8
 /        /  
1        7   9

输出：[1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]

 1
  
   2
    
     3
      
       4
        
         5
          
           6
            
             7
              
               8
                
                 9   

提示：

1. 给定树中的结点数介于 1 和 100 之间。
2. 每个结点都有一个从 0 到 1000 范围内的唯一整数值。

---

Runtime: 88 ms

Memory Usage: 19.4 MB

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public var val: Int
 *     public var left: TreeNode?
 *     public var right: TreeNode?
 *     public init(_ val: Int) {
 *         self.val = val
 *         self.left = nil
 *         self.right = nil
 *     }
 * }
 */
class Solution {
    func increasingBST(_ root: TreeNode?) -> TreeNode? {
        return increasingBST(root, nil)
    }

    func increasingBST(_ root:TreeNode?,_ tail:TreeNode?) -> TreeNode? {
        if root == nil {return tail}
        var res:TreeNode? = increasingBST(root?.left, root)
        root?.left = nil
        root?.right = increasingBST(root?.right, tail)
        return res
    }
}

---

88ms

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public var val: Int
 *     public var left: TreeNode?
 *     public var right: TreeNode?
 *     public init(_ val: Int) {
 *         self.val = val
 *         self.left = nil
 *         self.right = nil
 *     }
 * }
 */
class Solution {
    func increasingBST(_ root: TreeNode?) -> TreeNode? {
        return increasingBST(root, nil)        
    }
    
    func increasingBST(_ root: TreeNode?, _ tail: TreeNode?) -> TreeNode? {
        guard let node = root else {
            return tail
        }        
        let left = increasingBST(node.left, node)
        node.left = nil
        node.right = increasingBST(node.right, tail)        
        return left
    }
}

---

96ms

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public var val: Int
 *     public var left: TreeNode?
 *     public var right: TreeNode?
 *     public init(_ val: Int) {
 *         self.val = val
 *         self.left = nil
 *         self.right = nil
 *     }
 * }
 */
class Solution {
    
    var newParent: TreeNode?
    var newRoot: TreeNode?
    
    func increasingBST(_ root: TreeNode?) -> TreeNode? {        
        inorder(root)        
        return newRoot
    }
    
    func inorder(_ root: TreeNode?) {
        guard let root = root else { return } 
        inorder(root.left)        
        if let newParent = newParent {
            root.left = nil
            newParent.right = root
        } else {
            newRoot = root
        }        
        newParent = root      
        inorder(root.right)
    }
}

---

100ms

class Solution {
    var list = [TreeNode?]()
    func increasingBST(_ root: TreeNode?) -> TreeNode? {
        inorder(root: root)
        let node = TreeNode.init(0)
        list.insert(node, at: 0)
        for i in 0..<list.count - 1 {
            list[i]?.left = nil
            list[i]?.right = list[i+1]
        }
        if list.count - 1 > 0 {
            list[list.count - 1]?.left = nil
        }
        return node.right
    }
    
    func inorder(root: TreeNode?) {
        var stack = [TreeNode]()
        var root = root
        while root != nil || stack.count > 0 {
            if root != nil {
                stack.append(root!)
                root = root?.left
            }else {
                let last = stack.removeLast()
                list.append(last)
                root = last.right
            }
        }
    }
}

---

104ms

class Solution {
    var newHead:TreeNode?
    var nextNode:TreeNode?
    
    
    func increasingBST(_ root: TreeNode?) -> TreeNode? {

        guard let root = root else
        {
            return nil
        }
        
        increasingBST(root.left)
        
        if newHead == nil
        {
            newHead = root
        }
        root.left = nil
        if nextNode != nil
        {
            nextNode?.right = root
        }
        nextNode = root
        
        increasingBST(root.right)
        return newHead
    }
}

---

108ms

class Solution {
    func increasingBST(_ root: TreeNode?) -> TreeNode? {
        guard let root = root else {
            return nil 
        }
        let resultTree = TreeNode(0)
        var current: TreeNode? = resultTree
        inorderTraversal(root) {
            val in 
            current?.right = TreeNode(val)
            current = current?.right
        }
        
        return resultTree.right
    }
}


func inorderTraversal(_ root: TreeNode?, _ visit: (Int) -> Void) {
    guard let root = root else {
        return 
    }
    inorderTraversal(root.left, visit)
    visit(root.val)
    inorderTraversal(root.right, visit)
}

---

116ms

class Solution {
    func increasingBST(_ root: TreeNode?) -> TreeNode? {
        var toReturn = getLeft(root)
        var r = root
        helper(r, nil)
        return toReturn
    }
    
    func getLeft(_ root: TreeNode?) -> TreeNode? {
        var root = root
        if root == nil { return nil }
        while root!.left != nil {
            root = root!.left
        }
        return root
    }
    
    func helper(_ root: TreeNode?, _ p: TreeNode?) -> TreeNode? {
        if root == nil { return p }
        let prev = helper(root!.left, p)
        let r = root!.right
        root!.left = nil
        if var prev = prev {
            prev.right = root
        }
        return helper(r, root)
    }
}

---

216ms

class Solution {
    func increasingBST(_ root: TreeNode?) -> TreeNode? {
       var arr = [Int]()
       midTree(root,&arr)
       if arr.count == 0 { return nil }
       else {
           var root = TreeNode(arr[0])
           var temp = root
           for index in 1..<arr.count {
               var right = TreeNode(arr[index])
               temp.right = right
               temp = right
           }
           return root
       }
    }

    func midTree(_ root: TreeNode?, _ arr: inout [Int]) {
        guard let root = root else { return }
        if root.left != nil { midTree(root.left,&arr) }
        arr.append(root.val)
        if root.right != nil {midTree(root.right,&arr)}
    }
}