104. 二叉树的最大深度BFS

/**
 * 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 maxDepth(TreeNode* root) {
        if(root==nullptr)return 0;
        auto q=vector<TreeNode*>();
        auto d=0;
        q.push_back(root);
        while(!q.empty()){
            ++d;
            auto sz=q.size();
            for(auto i=0;i<sz;++i){
                auto t=q.front();
                q.erase(q.begin());
                if(t->left!=nullptr)q.push_back(t->left);
                if(t->right!=nullptr)q.push_back(t->right);
            }
        }
        return d;
    }
};