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main3.cpp
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/// Source : https://leetcode.com/problems/average-of-levels-in-binary-tree/description/
/// Author : liuyubobobo
/// Time : 2018-06-03
#include <iostream>
#include <vector>
#include <cassert>
using namespace std;
/// Definition for a binary tree node.
struct TreeNode {
int val;
TreeNode *left;
TreeNode *right;
TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
/// DFS
/// Time Complexity: O(n)
/// Space Complexity: O(n)
class Solution {
public:
vector<double> averageOfLevels(TreeNode* root) {
vector<double> res;
if(root == NULL)
return res;
vector<int> count;
dfs(root, 0, res, count);
assert(res.size() == count.size());
for(int i = 0 ; i < res.size() ; i ++)
res[i] /= count[i];
return res;
}
private:
void dfs(TreeNode* node, int level, vector<double>& res, vector<int>& count){
if(node == NULL)
return;
if(level < res.size()){
res[level] += (double)node->val;
assert(level < count.size());
count[level] += 1;
}
else{
res.push_back((double)node->val);
count.push_back(1);
assert(res.size() == count.size());
}
dfs(node->left, level + 1, res, count);
dfs(node->right, level + 1, res, count);
}
};
int main() {
return 0;
}