Description:
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.
/**
* 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) {
List <Double> result = new ArrayList<>();
Queue<TreeNode> test = new LinkedList<>();
test.add(root);
while (!test.isEmpty()){
int num = test.size();
double sum = 0.0;
for (int i = 0; i < num; i++) {
TreeNode x = test.poll();
sum = sum + x.val;
if (x.left != null)
test.add(x.left);
if (x.right != null)
test.add(x.right);
}
result.add(sum/num);
}
return result;
}
}
p.s. 这里使用了queue来统计每一层element的个数!