leetcode
January 14, 2024

Viiisit [LeetCode] - 226. Invert Binary Tree

#php#javascript#ruby

keep learning, keep coding!

Problem - Invert Binary Tree

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

翻譯蒟蒻

對一個二元樹進行反轉操作（反轉就是將每個節點的左右子樹交換位置），並返回反轉後的二元樹的根節點。

如果原始的二元樹是這樣的：

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    1
   / \
  2   3
 / \
4   5

經過反轉後，樹的結構變為：

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5
  1
 / \
3   2
   / \
  5   4

使用遞迴，對樹的每一個節點進行左右子樹的交換操作，一直迭代到樹的底部。

Solution - JavaScript

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/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {TreeNode}
 */
var invertTree = function(root) {
  if(root === null) return null;

  let left = invertTree(root.left);
  let right = invertTree(root.right);

  root.left = right;
  root.right = left;

  return root;
};

Solution - Ruby

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def invert_tree(root)
  return nil if root.nil?
  root.left, root.right = root.right, root.left
  invert_tree(root.left)
  invert_tree(root.right)
  root
end

Solution - PHP

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function invertTree($root) {
    if ($root == null) {
        return null;
    }
    $left = $this->invertTree($root->left);
    $right = $this->invertTree($root->right);
    $root->left = $right;
    $root->right = $left;
    return $root;
}

LeetCode 傳送門 - Invert Binary Tree