二叉树3---求每层结点的均值

秒速五厘米 2022-05-25 11:27 159阅读 0赞

1、题目：

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].

2、解答：我个人感觉广度优先遍历的思路容易解决此题.

3、C++代码：

class Solution {
    public:
        vector<double> averageOfLevels(TreeNode* root) {
            vector<double> result;
            queue<TreeNode *> q;
            q.push(root);
            while(!q.empty()){
                long sum = 0;
                int len = q.size();
                for(int i=0;i<len;i++){
                    TreeNode *temp = q.front();
                    q.pop();
                    if(temp->left)
                        q.push(temp->left);
                    if(temp->right)
                        q.push(temp->right);sum += temp->val;
                    
                    
                }
                result.push_back((double)sum/len);
            }
            return result; 
        }
    };

python代码：

class Solution:
        def averageOfLevels(self, root):
            """
            :type root: TreeNode
            :rtype: List[float]
            """
            result = []
            if root == None:
                return result
            
            q = [root]
            while q:
                q1 = []
                sum = 0
                len = 0
                while q:
                    temp = q.pop()
                    if temp.left:
                        q1.append(temp.left)
                    if temp.right:
                        q1.append(temp.right)
                    sum += temp.val
                    len += 1
                result.append(sum*1.0/len)
                q = list(q1)
            return result