103. 二叉树的锯齿形层序遍历

103. 二叉树的锯齿形层序遍历

题目链接：103. 二叉树的锯齿形层序遍历

代码如下：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
   
public:
    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
   
        vector<vector<int>> res;
        int count=0;

        if(root==nullptr)
            return res;
        queue<TreeNode*> que;
        que.push(root);

        //层次遍历
        while(!que.empty())
        {
   
            int len=que.size();
            vector<int> temp;

            for(int i=0;i<len;i++)
            {
   
                root=que.front();
                que.pop();

                temp.push_back(root->val);
                if(root->left)
                    que.push(root->left);
                if(root->right) 
                    que.push(root->right);
            }

            if(count%2==1)
                reverse(temp.begin(),temp.end());
            count++;
            res.push_back(temp);
        }

        return res;
    }
};