LeetCode-Java-637. Average of Levels in Binary Tree

题目

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].
Note:
The range of node's value is in the range of 32-bit signed integer.

代码

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<Double> averageOfLevels(TreeNode root) {
        ArrayList<Double> list = new  ArrayList<Double>();
        LinkedList<TreeNode> tree = new LinkedList<TreeNode>();
        tree.add(root);
        double sum = 0;
        while(!tree.isEmpty()){
            int n = tree.size();
            sum = 0;
            for(int i=0;i<n;i++){
                TreeNode node = tree.removeFirst();
                sum+=node.val;
                if(node.left!=null){
                    tree.addLast(node.left);
                }
                if(node.right!=null){
                    tree.addLast(node.right);
                }
            }
            list.add(sum/n);
        }
        return list;
    }
}

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<Double> averageOfLevels(TreeNode root) {
        ArrayList<Double> list = new  ArrayList<Double>();
        LinkedList<TreeNode> tree = new LinkedList<TreeNode>();
        tree.add(root);
        double sum = 0;
        while(!tree.isEmpty()){
            int n = tree.size();
            sum = 0;
            for(int i=0;i<n;i++){
                TreeNode node = tree.removeFirst();
                sum+=node.val;
                if(node.left!=null){
                    tree.addLast(node.left);
                }
                if(node.right!=null){
                    tree.addLast(node.right);
                }
            }
            list.add(sum/n);
        }
        return list;
    }
}