[Swift]LeetCode669. 修剪二叉搜索树 | Trim a Binary Search Tree

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Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.

Example 1:

Input: 
    1
   / \
  0   2

  L = 1
  R = 2

Output: 
    1
      \
       2 

Example 2:

Input: 
    3
   / \
  0   4
   \
    2
   /
  1

  L = 1
  R = 3

Output: 
      3
     / 
   2   
  /
 1

---

给定一个二叉搜索树，同时给定最小边界L 和最大边界 R。通过修剪二叉搜索树，使得所有节点的值在[L, R]中 (R>=L) 。你可能需要改变树的根节点，所以结果应当返回修剪好的二叉搜索树的新的根节点。

示例 1:

输入: 
    1
   / \
  0   2

  L = 1
  R = 2

输出: 
    1
      \
       2

示例 2:

输入: 
    3
   / \
  0   4
   \
    2
   /
  1

  L = 1
  R = 3

输出: 
      3
     / 
   2   
  /
 1

---

68ms

/**
 * 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 trimBST(_ root: TreeNode?, _ L: Int, _ R: Int) -> TreeNode? {
        guard let r = root else { return nil }
        
        if r.val > R { return trimBST(r.left, L, R) }
        if r.val < L { return trimBST(r.right, L, R) }
        
        r.left = trimBST(r.left, L, R)
        r.right = trimBST(r.right, L, R)
        
        return r
    }
}

---

84ms

/**
 * 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 trimBST(_ root: TreeNode?, _ L: Int, _ R: Int) -> TreeNode? {
        guard let root = root else {
            return nil 
        }
        
        var resultTree: TreeNode? = nil 
        preorderTraversal(root) {
            val in 
            if val >= L && val <= R {
                resultTree = addNode(resultTree, val)
            }
        }
        return resultTree
    }
}

func addNode(_ root: TreeNode?, _ val: Int) -> TreeNode {
    guard let root = root else {
        return TreeNode(val)
    }
    
    if val <= root.val {
        root.left = addNode(root.left, val)
    } else {
        root.right = addNode(root.right, val)
    }
    return root
}

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

---

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 {
    func trimBST(_ root: TreeNode?, _ L: Int, _ R: Int) -> TreeNode? {
        guard let r = root else {
            return nil 
        }
        if r.val < L {
            return trimBST(r.right, L, R)
        } else if r.val > R {
            return trimBST(r.left, L, R)
        }
        r.left = trimBST(r.left, L, R)
        r.right = trimBST(r.right, L, R)
        return r
    }
    
    func deleteNode(_ node: TreeNode) -> TreeNode?{
        if node.left == nil {
            return node.right
        } else if node.right == nil {
            return node.left
        } else {
            return insert(root: node.left, node: node.right!)
        }
    }
    
    func insert(root: TreeNode?, node: TreeNode) -> TreeNode {
        guard var n = root else {
            return node
        }
        
        if node.val < n.val {
            if n.left == nil {
                n.left = node
            } else {
                n.left = insert(root: n.left, node: node)
            }
        } else {
            if n.right == nil {
                n.right = node
            } else {
                n.right = insert(root: n.right, node: node)
            }
        }
        
        return node
    }
}