LeetCode 102二叉树的层次遍历 队列

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
        vector<vector<int>>ans;
        TreeNode *top=NULL;
        if(root==NULL)return ans;
        queue<TreeNode*>myqueue;
        myqueue.push(root);
        while(!myqueue.empty())
        {
             vector<int>temp;
            int num = myqueue.size();
            for(int i= 0;i < num;i++){
            top=myqueue.front();
            myqueue.pop();
           
            temp.push_back(top->val);
                if(top->left!=NULL)
                {
                    myqueue.push(top->left);
                }
                if(top->right!=NULL)
                    myqueue.push(top->right);
            }
            ans.push_back(temp);
        }
        return ans;
    }
};