Leetcode 103 Solution

This article provides solution to leetcode question 103 (binary-tree-zigzag-level-order-traversal)
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https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal

Solution

/**
 * 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>> zigzagLevelOrder(TreeNode* root) {
        vector<vector<int>> res;
        queue<TreeNode*> q;

        if (root == NULL)
            return res;

        bool dir = true;

        q.push(root);

        while (q.empty() == false)
        {
            vector<TreeNode*> v1;
            vector<int> v2;

            while (q.empty() == false)
            {
                v1.push_back(q.front());
                q.pop();
            }

            for (auto it = v1.begin(); it != v1.end(); it++)
            {
                if ((*it)->left)
                    q.push((*it)->left);
                if ((*it)->right)
                    q.push((*it)->right);
            }

            if (dir)
            {
                for (auto it = v1.begin(); it != v1.end(); it++)
                {
                    v2.push_back((*it)->val);
                }
            }
            else if (dir == false)
            {
                for (auto it = v1.rbegin(); it != v1.rend(); it++)
                {
                    v2.push_back((*it)->val);
                }
            }

            res.push_back(v2);

            dir = !dir;
        }

        return res;
    }
};