1 class Solution {

 2 public:

 3     vector<int>res;

 4     void InOrder(TreeNode* p){

 5         if(p!=NULL){

 6             InOrder(p->left);

 7             res.push_back(p->val);

 8             InOrder(p->right);

 9         }

10     }

11     int getMinimumDifference(TreeNode* root) {

12        InOrder(root);

13        int min = INT_MAX;

14        for(int i = 0;i < res.size() - 1;i++){

15            if(abs(res[i]-res[i+1]) < min )

16                 min = abs(res[i]-res[i+1]);

17        }

18        return min;

19     }

20

21 };

 1 class Solution {

 2 public:

 3     int res = INT_MAX;

 4     TreeNode* pre;

 5     void InOrder(TreeNode* root){

 6         if(root!= NULL) {

 7             InOrder(root->left);

 8             if(pre!=NULL) res = min(res,root->val - pre->val);

 9             pre = root;

10             InOrder(root->right);

11         }

12     }

13

14     int getMinimumDifference(TreeNode* root) {

15         InOrder(root);

16         return res;

17     }

18

19 };