[数据结构与算法]563. 二叉树的坡度

?链接：

563. 二叉树的坡度

题解：

/**
 * 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 sum = 0;
        dfs(sum, root);
        return sum;
    }
    int dfs(int& sum, TreeNode* root) {
        if (!root) {
            return 0;
        }
        int left = dfs(sum, root->left);
        int right = dfs(sum, root->right);
        sum += abs(left-right);
        return left+right+root->val;
    }
};