226.Invert-Binary-Tree.md

226. Invert Binary Tree

題目

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Given the root of a binary tree, invert the tree, and return its root.

Example 1:

Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]

Example 2:

Input: root = [2,1,3]
Output: [2,3,1]

Example 3:

Input: root = []
Output: []

Constraints:

• The number of nodes in the tree is in the range [0, 100].
• 100 <= Node.val <= 100

思路

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Code

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• PHP

  Runtime 4ms Beats 76.82% of users with PHP

  Memory 19.64 MB Beats 96.03% of users with PHP

  /**
   * Definition for a binary tree node.
   * class TreeNode {
   *     public $val = null;
   *     public $left = null;
   *     public $right = null;
   *     function __construct($val = 0, $left = null, $right = null) {
   *         $this->val = $val;
   *         $this->left = $left;
   *         $this->right = $right;
   *     }
   * }
   */
  class Solution {
  
      /**
       * @param TreeNode $root
       * @return TreeNode
       */
      function invertTree($root) {
          if (is_null($root)) {
              return $root;
          } 
  
          $tmp = $this->invertTree($root->left);
          $root->left = $this->invertTree($root->right);
          $root->right = $tmp;
          
          return $root;
      }
  }

• GoLang

  Runtime 0 ms Beats 100%

  Memory 2.2 MB Beats 10.77%

  /**
   * Definition for a binary tree node.
   * type TreeNode struct {
   *     Val int
   *     Left *TreeNode
   *     Right *TreeNode
   * }
   */
  func invertTree(root *TreeNode) *TreeNode {
      if root == nil {
          return root
      }
      
      root.Left, root.Right = invertTree(root.Right), invertTree(root.Left)
  
      return root
  }

Reference

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