637. Average of Levels in Binary Tree

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

static int wing=[]()
{
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution 
{
public:
    vector<double> averageOfLevels(TreeNode* root) 
    {
        queue<TreeNode*> q;
        TreeNode* p=root;
        q.push(p);
        vector<double> res;
        while(!q.empty())
        {
            int sz=q.size();
            double sum=0.0;
            for(int i=0;i<sz;i++)
            {
                p=q.front();
                sum+=p->val;
                if(p->left!=NULL)
                    q.push(p->left);
                if(p->right!=NULL)
                    q.push(p->right);
                q.pop();
            }
            res.push_back(sum/sz);
        }
        return res;
    }
};

层次遍历，问题不大