题目：

题解：

class Solution {
public:int minDepth(TreeNode *root) {if (root == nullptr) {return 0;}queue<pair<TreeNode *, int> > que;que.emplace(root, 1);while (!que.empty()) {TreeNode *node = que.front().first;int depth = que.front().second;que.pop();if (node->left == nullptr && node->right == nullptr) {return depth;}if (node->left != nullptr) {que.emplace(node->left, depth + 1);}if (node->right != nullptr) {que.emplace(node->right, depth + 1);}}return 0;}
};