題目描述

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.

題目要求計算一棵二叉樹的高度。本題最簡單的解法是遞迴計算左右子樹的高度，並在左右子樹高度的最大值的基礎上加1，則得到本層到葉子節點的高度。

解題程式碼

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

        int left = 0, right = 0;
        if (root != NULL)
        {
            if
 
(root->left != NULL)
                left = maxDepth(root->left);
            if(root->right != NULL)
                right = maxDepth(root->right);
        }
        return max(left,right)+1;
    }
};