題目
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.
答案
class Solution {
public List<Double> averageOfLevels(TreeNode root) {
List<Double> list = new ArrayList<Double>();
if(root == null) return list;
Queue<TreeNode> q = new LinkedList<TreeNode>();
q.offer(root);
while(q.size() != 0) {
int curr_size = q.size();
double average = 0;
for(int i = 0; i < curr_size; i++) {
TreeNode t = q.poll();
average += t.val;
if(t.left != null) q.offer(t.left);
if(t.right != null) q.offer(t.right);
}
list.add(average / curr_size);
}
return list;
}
}
