[LeetCode] 637. Average of Levels in Binary Tree

轉自LeetCode

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:

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

<Solution>

想法如下

• 用 level traversal 歷遍 tree，然後計算總和找出平均即可

• 要注意總和可能會超過 integer 的範圍

code 如下

Java