leetcode刷题笔记——树的广度优先遍历

模板：

public:
    vector<int> decorateRecord(TreeNode* root) {
        vector<int> res;
        if(!root) return res;
        queue que;
        que.push(root);
        while(!que.empty()){
            TreeNode* node = que.front();
            que.pop();
            res.push_back(node->val);
            if(node->left) que.push(node->left);
            if(node->right) que.push(node->right);
        }
        return res;
    }

public: 
     vectorint>> levelOrder(TreeNode* root) {
        queue q;
        if(root) q.push(root);
        vectorint>> result;
        while(!q.empty()){
            int size=q.size();
            //每层定义一个path路径
            vector<int> path;
//这里一定要用固定大小size，不要使用q.size()，因为q.size()是不断变化的
            for(int i=0;i
                TreeNode* node=q.front();
                path.push_back(node->val);
                q.pop();
                if(node->left) q.push(node->left);
                if(node->right) q.push(node->right);
            }
            result.push_back(path);
        }
        return result;
    }