题目链接/文章讲解/视频讲解：https://programmercarl.com/0111.%E4%BA%8C%E5%8F%89%E6%A0%91%E7%9A%84%E6%9C%80%E5%B0%8F%E6%B7%B1%E5%BA%A6.html

1.还是递归先做第一遍，后续队列在迭代做一次。

CPP

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int getMin(TreeNode *node){
        if(node == NULL)return 0;
        int leftDepth = getMin(node->left);
        int rigthDepth = getMin(node->right);
        if(node->left == NULL && node->right != NULL)return 1+rigthDepth;
        if(node->right == NULL && node->left != NULL)return 1+leftDepth;
        int res = 1 + min(leftDepth,rigthDepth);
        return res;
    }
    int minDepth(TreeNode* root) {
        return getMin(root);
    }
};