fgb

/**
 * 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 minDepth(TreeNode* root) {
        if(root == nullptr) {
            return 0;
        } else {
            // return min( minDepth(root->left), minDepth(root->right)) + 1;
            int leftnum = 1e9, rightnum = 1e9;
            if(root->left == nullptr && root->right == nullptr) return 1;
            if(root->left != nullptr) leftnum = minDepth(root->left);
            if(root->right != nullptr) rightnum = minDepth(root->right);
            return min(leftnum, rightnum) + 1;
        }
    }
};