题解 | #求二叉树的层序遍历#

class Solution {
public:
    /**
     * 
     * @param root TreeNode类 
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > levelOrder(TreeNode* root) {
        queue<TreeNode* > q;
        vector<vector<int> > result;
        if(root)
            q.push(root);
        while(!q.empty())
        {
            int n=q.size();
            vector<int> v;
            while(n--)
            {
                TreeNode* p=q.front();
                q.pop();
                v.push_back(p->val);
                if(p->left)
                    q.push(p->left);
                if(p->right)
                    q.push(p->right);
            }
            result.push_back(v);
        }
        return result;
    }
};

注意考虑空树，