LeetCode 563. 二叉樹的坡度（遞歸、前序遍歷）

二叉樹的坡度

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int findTilt(TreeNode* root) {
        getSum(root);
        return preOrder(root);
    }

    int preOrder(TreeNode *root){
        if(!root){
            return 0;
        }
        return getTilt(root)+preOrder(root->left)+preOrder(root->right);
    }

    int getTilt(TreeNode *root){
        if(!root){
            return 0;
        }
        int lsum = !(root->left)?0:root->left->val;
        int rsum = !(root->right)?0:root->right->val;
        return abs(lsum-rsum);
    }

    int getSum(TreeNode *root){
        if(!root){
            return 0;
        }
        return root->val += getSum(root->left)+getSum(root->right);
    }
};