class Solution { public: int maxDepth(TreeNode* root) { // write code here if(!root) return 0; queue<TreeNode*> q; q.push(root); int hight=0; while(!q.empty()) { ++hight; int n = q.size(); for(int i=0;i<n;++i) { TreeNode* temp = q.front(); q.pop(); if(temp->left) q.push(temp->left); if(temp->right) q.push(temp->right); } } return hight; } };