# 111. Minimum Depth of Binary Tree

## 1.問題

* 找出最小高度

![](https://901207480-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LGKoChvN9am4__HCIRK%2F-LNL17k7UO9Z0MeZenA3%2F-LNL20iZ4rFrkLe2NIt9%2F%E8%9E%A2%E5%B9%95%E5%BF%AB%E7%85%A7%202018-09-26%20%E4%B8%8B%E5%8D%889.22.37.png?alt=media\&token=0d34fff3-9e3b-4550-85fe-2dcceeaf595a)

## 2.想法

* 提問確認題意:  
  * binary tree的類型
* function header, parameter
* test input
* 觀察
* 說明想法
  * 如果不判斷left, right, 就將node丟下去迭代, 這樣會出現一些side effect
  * 比較好的做法是判斷
    * left, right皆不存在時, sum == root->val?
    * left存在時才繼續迭代
    * right存在時才繼續迭代
    * 皆否則return false
* 測試計算複雜度

## 3.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 minDepth(TreeNode* root) {
        if (!root) {
            return 0;
        }
        
        if (root->left && !root->right){
            return minDepth(root->left) + 1;
        } else if (root->right && !root->left){
            return minDepth(root->right) + 1;
        }
        
        return min(minDepth(root->left), minDepth(root->right)) + 1;
    }
};
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://jenhsuan.gitbook.io/algorithm/leetcode/111.-minimum-depth-of-binary-tree.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.