637 Average of Levels in Binary Tree

637 Average of Levels in Binary Tree

// Double sum = 0.0; not int sum = 0;



class Solution {
    public List<Double> averageOfLevels(TreeNode root) {
    Queue<TreeNode> queue = new LinkedList<>();
    List<Double> result = new ArrayList<>();
    queue.offer(root);
    while(!queue.isEmpty()){
      int size = queue.size();
      Double sum = 0.0; // Double sum = 0.0; not int sum = 0;
      for(int i = 0; i < size; i++){
        TreeNode cur = queue.poll();
        sum += cur.val;
        if(cur.left != null) queue.offer(cur.left);
        if(cur.right != null) queue.offer(cur.right);
      }
      result.add(sum / size);
    }
    return result;
  }
}

 Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.

Example 1:

Input:
    3
   / \
  9  20
    /  \
   15   7
Output: [3, 14.5, 11]
Explanation:
The average value of nodes on level 0 is 3,  on level 1 is 14.5, and on level 2 is 11. Hence return [3, 14.5, 11].