Viiisit [LeetCode] - 104. Maximum Depth of Binary Tree

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Problem - Maximum Depth of Binary Tree

Given the root of a binary tree, return its maximum depth.

A binary tree’s maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

翻譯蒟蒻

計算二元樹的最大深度。

• Example 1:

  Input: root = [3,9,20,null,null,15,7]
  Output: 3

• Example 2:

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

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使用遞迴方式來找出二元樹的最大深度。

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Solution - JavaScript

/**
 * 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 {number}
 */
var maxDepth = function(root) {
  if (root === null) {
    return 0;
  }
  let left = maxDepth(root.left);
  let right = maxDepth(root.right);
  return Math.max(left, right) + 1;
};

Solution - Ruby

def max_depth(root)
  return 0 if root.nil?
  left = max_depth(root.left)
  right = max_depth(root.right)
  return 1 + [left, right].max
end

Solution - PHP

function maxDepth($root) {
  if ($root === null) return 0;

  $left = $this->maxDepth($root->left);
  $right = $this->maxDepth($root->right);
  return max($left, $right) + 1;
}

LeetCode 傳送門 - Maximum Depth of Binary Tree