Competitive_Programming/LeetCode/Full_List/103.cpp at master · Ravi-Maurya/Competitive_Programming · GitHub

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/**
 * 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) {
        deque<TreeNode*> traverse;
        int dir = 1;
        vector<vector<int>> res;
        if(!root)
            return res;
        traverse.push_back(root);
        while(!traverse.empty()){
            int size = traverse.size();
            vector<int> tmp;
            while(size--){
                if(dir){
                    auto curr = traverse.front();
                    traverse.pop_front();
                    tmp.push_back(curr->val);
                    if(curr->left)
                        traverse.push_back(curr->left);
                    if(curr->right)
                        traverse.push_back(curr->right);
                }
                else{
                    auto curr = traverse.back();
                    traverse.pop_back();
                    tmp.push_back(curr->val);
                    if(curr->right)
                        traverse.push_front(curr->right);
                    if(curr->left)
                        traverse.push_front(curr->left);
                }
            }
            if(tmp.size())
                res.push_back(tmp);
            dir ^= 1;
        }
        return res;
    }
};


/**
 * 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:

    void dfs(TreeNode* root, int level, vector<vector<int>>& res){
        if(level>=res.size()){
            vector<int> tmp = {root->val};
            res.push_back(tmp);
        }
        else{
            if(level%2 == 0)
                res[level].push_back(root->val);
            else
                res[level].insert(res[level].begin(),root->val);
        }
        if(root->left)
            dfs(root->left,level+1,res);
        if(root->right)
            dfs(root->right,level+1,res);
        return;
    }

    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
        vector<vector<int>> res;
        if(!root)
            return res;
        dfs(root,0,res);
        return res;
    }
};