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max-level-sum-of-binary-tree.dart (1224B)

      1 //Given a binary tree return the layer with the greatest 
      2 //value where the value is the sum of all nodes on that layer.
      3 
      4 //First I did DFS to create a layer list. Normally people do this with
      5 //BFS, but leetcode does not have priority queues in dart so this is technically faster.
      6 //Then from there I found the layer with the highest sum and returned the index of it + 1.
      7 
      8 //Time: 393ms Beats: 100%
      9 //Memory: 181.5MB Beats: 100%
     10 
     11 class Solution {
     12     List<List<int>> layers = [];
     13   int maxLevelSum(TreeNode? root) {
     14       recurse(0, root);
     15       int max = -200000000;
     16       int max_layer = 1;
     17       int layer_count = 1;
     18       print(layers);
     19       for(var list in layers){
     20           int current = 0;
     21           for(int val in list){
     22               current += val;
     23           }
     24           if(current > max){
     25               max = current;
     26               max_layer = layer_count;
     27           }
     28           layer_count += 1;
     29       }
     30       return max_layer;
     31   }
     32 
     33   void recurse(int depth, TreeNode? root){
     34       if(root == null){
     35           return;
     36       }
     37       if(depth >= layers.length){
     38           layers.add([]);
     39       }
     40       layers[depth].add(root.val);
     41       recurse(depth+ 1 ,root.left);
     42       recurse(depth + 1 ,root.right);
     43   }
     44 }