Leetcode/leetcode103.cpp at main · ksaini-web/Leetcode · GitHub

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/**
 * 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>> result;

        if(!root) return result;

        queue<TreeNode* >q;


        q.push(root);

        bool lefttoright = true;

        while(!q.empty()){

        int size = q.size();

        vector<int>level(size);

        for(int i = 0;i<size;i++){

            TreeNode* node = q.front();

            q.pop();


            int index =   lefttoright? i :(size -1-i);

            level[index] = node->val;

            if(node->left) q.push(node->left);
            if(node->right) q.push(node->right);
        }

          lefttoright =!  lefttoright;
          result.push_back(level);


        }

        return result;

    }
};