Title

the problem link

Given a Binary Search Tree (BST) with the root node root, return the minimum difference between the values of any two different nodes in the tree.

Example :

Input: root = [4,2,6,1,3,null,null] Output: 1 Explanation: Note that root is a TreeNode object, not an array.

The given tree [4,2,6,1,3,null,null] is represented by the following diagram:

      4
    /   \
  2      6
 / \    
1   3  

while the minimum difference in this tree is 1, it occurs between node 1 and node 2, also between node 3 and node 2. Note:

The size of the BST will be between 2 and 100. The BST is always valid, each node’s value is an integer, and each node’s value is different.

这一摸一样嘛！！！

Solution

//cpp:
/**
 * 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 minn=INT_MAX,val=-1;
    int getMinimumDifference(TreeNode* root) {
        if(root->left) getMinimumDifference(root->left);
        if(val>=0) minn=min(minn,abs(root->val-val));
        val=root->val;
        if(root->right) getMinimumDifference(root->right);
        return minn;
    }
    
    int minDiffInBST(TreeNode* root) {
        return getMinimumDifference(root);
    }
};