【leetcode】563. 二叉树的坡度

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

int findTilt(struct TreeNode* root){
    int sum=0;
    recursion(root,&sum);
    return sum;
}