637 Average of Levels in Binary Tree
Problem
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.
Solutions
/**
* 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> res = new LinkedList<Double>();
Queue<TreeNode> q = new LinkedList<TreeNode>();
if (root == null) {
return res;
}
q.add(root);
while (!q.isEmpty()) {
int n = q.size();
double sum = 0;
for (int i = 0; i < n; i ++) {
TreeNode node = q.poll();
sum += (double)node.val;
if (node.left != null) {
q.add(node.left);
}
if (node.right != null) {
q.add(node.right);
}
}
res.add(sum/(double)n);
}
return res;
}
}