[leetcode] Binary Tree Level Order Traversal

Binary Tree Level Order Traversal

使用两个队列

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {private:    vector<vector<int>> res;public:    vector<vector<int> > levelOrder(TreeNode *root) {        if (root==NULL) {            return res;        }        queue<TreeNode*> curQ,nextQ;        curQ.push(root);                while (!curQ.empty()) {            vector<int> layerRes;            while (!curQ.empty()) {                TreeNode *tmp=curQ.front();                layerRes.push_back(tmp->val);                curQ.pop();                if (tmp->left!=NULL) {                    nextQ.push(tmp->left);                }                if (tmp->right!=NULL) {                    nextQ.push(tmp->right);                }            }            curQ=nextQ;            while (!nextQ.empty()) {//清空                nextQ.pop();            }            res.push_back(layerRes);        }        return res;    }};

参考：

Binary Tree Level Order Traversal