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:
使用队列的先进先出的特点：
1 class Solution { 2 public: 3 vector<double> averageOfLevels(TreeNode* root) { 4 vector<double> ret; 5 queue<TreeNode*> q; 6 q.push(root); 7 while (!q.empty()) { 8 long long t = 0; 9 int n = q.size(); 10 for (int i = 0; i < n; i++) { 11 auto node = q.front(); 12 q.pop(); 13 if (node->left) q.push(node->left); 14 if (node->right) q.push(node->right); 15 t += node->val; 16 } 17 ret.push_back(double(t)/double(n)); 18 } 19 return ret; 20 } 21 };
LeetCode: 637 Average of Levels in Binary Tree
原文：http://www.cnblogs.com/llxblogs/p/7421573.html