0111. 二叉树的最小深度 [Easy] [Minimum Depth of Binary Tree].md

111. Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7

return its minimum depth = 2.

---

题目：二叉树的最小深度。从根结点到叶节点。

思路：同104. Maximum Depth of Binary Tree。

工程代码下载

/**
 * 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 == nullptr)
            return 0;
        int left = minDepth(root->left);
        int right = minDepth(root->right);

        // 注意这里需要判断是否为空的情况，同maxDepth的区别
        if(left == 0 || right == 0)
            return left + right + 1;
        else
            return min(left, right) + 1;
    }
};