二叉树的坡度

/**
 * 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 ans=0;
    int findTilt(TreeNode* root) {
        dfs(root);
        return ans;
 
    }
    int dfs(TreeNode*node)
    {
        if(node==nullptr)
        {
            return 0;
        }
         int sumleft=dfs(node->left);
         int sumright=dfs(node->right);
         ans+=abs(sumleft-sumright);
         return sumright+sumleft+node->val;
 
    }
};