leetcode

Leetcode submissions
git clone git://git.laack.co/leetcode.git
Log | Files | Refs | README

zig-zag-level-order.dart (1414B)

      1 //Traverse a binary tree and return a list that contains
      2 //one list for each layer. As you make your way down the tree
      3 //start going from left to right and then from right to left and so on.
      4 //The time complexity of this code is O(n) where n is the 
      5 //number of nodes in the tree.
      6 //Time: 264ms Beats: 63.64%
      7 //Memory: 143.1MB Beats: 54.55%
      8 
      9 /**
     10  * Definition for a binary tree node.
     11  * class TreeNode {
     12  *   int val;
     13  *   TreeNode? left;
     14  *   TreeNode? right;
     15  *   TreeNode([this.val = 0, this.left, this.right]);
     16  * }
     17  */
     18 class Solution {
     19   List<List<int>> zigzagLevelOrder(TreeNode? root) {
     20       if(root == null){
     21           return [];
     22       }
     23       List<TreeNode?> queue = [];
     24       List<List<int>> return_list = [];
     25       queue.add(root);
     26       int row = 0;
     27       while(queue.length > 0){
     28           return_list.add([]);
     29         int init_length = queue.length;
     30         for(int i = 0 ; i < init_length ; ++i){
     31             if(queue[0]?.left != null){
     32                 queue.add(queue[0]?.left);
     33             }
     34             if(queue[0]?.right != null){
     35                 queue.add(queue[0]?.right);
     36             }
     37             return_list[return_list.length - 1].add((queue[0]?.val ?? 0));
     38             queue.removeAt(0);
     39         }
     40         row += 1;
     41       }
     42 
     43       for(int i = 1 ; i < return_list.length ; i += 2){
     44           return_list[i] = return_list[i].reversed.toList();
     45       }
     46 
     47 
     48 
     49       return return_list;
     50 
     51   }
     52 
     53 }