[LeetCode] 102. Binary Tree Level Order Traversal - c++

큐를 사용한 BFS풀이 + 트리 노드

class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
        queue <TreeNode*> q;
        if(root==nullptr) {return {};}
        vector<vector<int>> ans;
        q.push(root);
        while(!q.empty()){
            int sz= q.size();
            vector<int> res;
            for(int i=0;i<sz;i++){
                TreeNode* temp = q.front();
                res.push_back(temp->val);
                q.pop();
                if(temp->left ) q.push(temp->left);
                if(temp->right) q.push(temp->right);
            }
            ans.push_back(res);
        }
        return ans;
    }
};

예외처리) root가 nullptr로 들어오는 경우 {}반환