[LeetCode] 637.Average of Levels in Binary Tree

[LeetCode] 637.Average of Levels in Binary Tree

• 题目描述
• 解题思路
• 实验代码

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题目描述

Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.

Example:
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.

解题思路

题目意思很好理解，就是找到每一层结点的值的和的平均值。这道题关键的难点是怎么找到同一层的结点。我这里使用了vector和queue两个容器，利用其中的相关操作就能解决这个问题，具体过程见代码。

实验代码

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<double> averageOfLevels(TreeNode* root) {
        vector<double> v;
        queue<TreeNode*> q;
        q.push(root);
        while (!q.empty()) {
            long temp = 0;
            int s = q.size();
            for (int i = 0; i < s; i++) {
                TreeNode* t = q.front();
                q.pop();
                if(t->left) q.push(t->left);
                if(t->right) q.push(t->right);
                temp += t->val;
            }
            v.push_back((double)temp/s);
        }
        return v;
    }
};