530. Minimum Absolute Difference in BST

Problem

Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes.

Example

Solution

BST中差值绝对值最小，只能出现在相邻节点。
本题与501题是类似的。

/**
 * 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 getMinimumDifference(TreeNode* root) {
            int ret = INT_MAX;
            TreeNode* pre = NULL;

            inOrder(root,pre,ret);

            return ret;
        
        

    }

    void inOrder(TreeNode* root,TreeNode* &pre,int &ret)
    {
        if(!root)
            return;
        inOrder(root->left,pre,ret);

        if(pre)
        {
            int curAD = abs(root->val - pre->val);
            if(curAD < ret)
            {
                ret = curAD;
            }
        }

        pre = root;

        inOrder(root->right,pre,ret);

    }
};