/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int findTilt(TreeNode* root) {
        int res = 0;
        help(root,res);
        return res;
    }
    
    int help(TreeNode *root, int &res){
        if (!root){
            return 0;
        }
        
        int left = help(root->left,res);
        int right = help(root->right,res);
        
        res+=abs(left-right);
        
        return root->val+left+right;
    }
};