【leetcode刷题】T146-二叉树的层平均值

示例 1:
输入:
    3
   / \
  9  20
    /  \
   15   7
输出: [3, 14.5, 11]
解释:
第0层的平均值是 3,  第1层是 14.5, 第2层是 11. 因此返回 [3, 14.5, 11].

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def averageOfLevels(self, root):
        """
        :type root: TreeNode
        :rtype: List[float]
        """
        p = [root]
        q = []
        res = []
        avg = 0
        count = 1
        while p or q:
            if not p:
                p = q
                q = []
                res.append(1.0 * avg / count)
                avg = 0
                count = len(p)
            node = p.pop()
            avg += node.val
            if node.left:
                q.append(node.left)
            if node.right:
                q.append(node.right)
        res.append(1.0 * avg / count)
        return res

/**
 * 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) {
        queue<TreeNode*> p;
        p.push(root);
        queue<TreeNode*> q;
        vector<double> res;
        double avg = 0;
        int count = 1;
        TreeNode* node = NULL;
        while(p.size() > 0 || q.size() > 0){
            if(p.size() == 0){
                while(q.size() != 0){
                    p.push(q.front());
                    q.pop();
                }
                res.push_back(1.0 * avg / count);
                avg = 0;
                count = p.size();
            }
            node = p.front();
            avg += node->val;
            p.pop();
            if(node->left)
                q.push(node->left);
            if(node->right)
                q.push(node->right);
        }
        res.push_back(1.0 * avg / count);
        return res;
    }
};