题解 | #求二叉树的层序遍历#

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class Solution {
public:
    vector<vector<int> > levelOrder(TreeNode* root) {
        // write code here
        if(!root) return {};
        vector<vector<int> > res;
        queue<TreeNode*> q;
        q.push(root);

        vector<int> line;
        while(!q.empty()){
            line.clear();
            int sz = q.size();
            for(int i=0; i<sz; ++i){
                TreeNode* cur = q.front();
                q.pop();
                line.push_back(cur->val);
                if(cur->left) q.push(cur->left);
                if(cur->right) q.push(cur->right);
            }
            res.push_back(line);
        }
        return res;
    }
};