1188. Minimum Absolute Difference in BST

描述

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

There are at least two nodes in this BST.

您在真实的面试中是否遇到过这个题？   是

样例

Input:

   1
    \
     3
    /
   2

Output:
1

Explanation:
The minimum absolute difference is 1, which is the difference between 2 and 1 (or between 2 and 3).

二叉搜索树BST的特点是左子树的值小于根节点，右子树的值大于根节点，所以进行中序遍历，得出每个根节点-左子树 和 右子树-根节点 的值 取其中的最小值即可。

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */

class Solution {
public:
    /**
     * @param root: the root
     * @return: the minimum absolute difference between values of any two nodes
     */
    int getMinimumDifference(TreeNode * root) {
        // Write your code here
        int res=INT_MAX;
        int pre=-1;
        inorder(root,pre,res);
        return res;
    }
    
    void inorder(TreeNode * root,int &pre,int &res){
        if(!root) return;
        inorder(root->left,pre,res); 
        if(pre!=-1) res=min(res,root->val-pre);
        pre=root->val;
        inorder(root->right,pre,res);
    }
};