[C#][LeetCode][Easy] 104. Maximum Depth of Binary Tree

心得：

這題是典型的遞迴題目，題目要求找到二元樹最深的層級為多少。

這題的解法很簡單，先宣告兩個變數分別來儲存左邊與右邊的層級，首先判斷左邊是否為空，若非為空值則會繼續搜尋此節點的子節點是否為空，搜尋完畢後再一併回傳至第一層的left變數裡，右邊反之，最後在比較左右兩邊哪個最大，最大的數字即為二元樹的層級。

問題：

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

答案：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int MaxDepth(TreeNode root) {
        if (root == null)
        {
            return 0;
        }

        int left = 1;
        int right = 1;

        if (root.left != null)
        {
            left += MaxDepth(root.left);
        }

        if (root.right != null)
        {
            right += MaxDepth(root.right);
        }

        return right > left ? right : left;
    }
}

參考：

1. https://skyyen999.gitbooks.io/-leetcode-with-javascript/content/questions/104md.html