Average of Levels in Binary Tree

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:

1. The range of node's value is in the range of 32-bit signed integer.

/**
 * 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> ans;
        vector<TreeNode*> q;
        vector<TreeNode*> next;
        if (root == NULL) {
            return ans;
        }
        q.push_back(root);
        ans.push_back(root -> val);
        long sum = 0;
        for (int i = 0; i < q.size(); i++) {
            TreeNode *tmp = q[i];
            if (tmp -> left) {
                next.push_back(tmp -> left);
                sum += tmp -> left -> val;
            }
            if (tmp -> right) {
                next.push_back(tmp -> right);
                sum += tmp -> right -> val;
            }
            if (i == q.size() - 1) {
                if (next.size() != 0) {
                    ans.push_back((double)sum / next.size());
                }
                q = next;
                next.clear();
                i = -1;
                sum = 0;
            }
        }
        return ans;
    }
};

============== USing queue and figure out the size in the beginning =====
class Solution { public: vector<double> averageOfLevels(TreeNode* root) { vector<double> values_to_return; if(root == nullptr) return values_to_return; queue<TreeNode*> levels; levels.push(root); values_to_return.push_back(root->val); int which_level = 0; while(!levels.empty()){ which_level = levels.size(); vector<double> tmp; while(which_level>0){ TreeNode * node = levels.front(); levels.pop(); if(node->left){ levels.push(node->left); tmp.push_back(node->left->val); } if(node->right){ levels.push(node->right); tmp.push_back(node->right->val); } which_level--; } double sum = 0; if(tmp.size()>0){ for(int i =0; i<tmp.size(); ++i){ sum = tmp[i]+sum; } values_to_return.push_back(sum/tmp.size()); } } return values_to_return; } };