783. Minimum Distance Between BST Nodes*

783. Minimum Distance Between BST Nodes*

https://leetcode.com/problems/minimum-distance-between-bst-nodes/

题目描述

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.

C++ 实现 1

中序遍历. 和 530. Minimum Absolute Difference in BST* 是同一题.

/**
 * 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 {
private:
    TreeNode *prev;
    int res = INT32_MAX;
    void inorder(TreeNode *root) {
        if (!root) return;
        inorder(root->left);
        if (prev) res = std::min(res, std::abs(root->val - prev->val));
        prev = root;
        inorder(root->right);
    }
public:
    int minDiffInBST(TreeNode* root) {
        inorder(root);
        return res;
    }
};