637. Average of Levels in Binary Tree
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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.
按层遍历,求每层平均值。
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ import java.util.LinkedList; import java.util.Queue; public class Solution { public List<Double> averageOfLevels(TreeNode root) { List<Double> retList = new ArrayList<Double>(); if (root == null) return retList; Queue<TreeNode> q = new LinkedList<TreeNode>(); q.offer(root); while ( ! q.isEmpty() ) { List<TreeNode> tl = new ArrayList<TreeNode>(); double sum = 0; while ( ! q.isEmpty() ) { TreeNode curr = q.poll(); tl.add(curr); sum += (double) curr.val; } retList.add(sum / tl.size()); for (TreeNode n : tl) { if (n.left != null) q.offer(n.left); if (n.right != null) q.offer(n.right); } } return retList; } }
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