783. Minimum Distance Between BST Nodes

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Problem

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

Example 1:

Input: root = [4,2,6,1,3]
Output: 1

Example 2:

Input: root = [1,0,48,null,null,12,49]
Output: 1

Constraints:

• The number of nodes in the tree is in the range [2, 100].
• 0 <= Node.val <= 10^5

Note: This question is the same as 530

Code

重复题目: 530

class Solution {
    Integer prev = null;
    int diff = Integer.MAX_VALUE;

    public int minDiffInBST(TreeNode root) {
        helper(root);

        return diff;
    }

    private void helper(TreeNode root){
        if(root == null) return;

        helper(root.left);

        if(prev == null){
            prev = root.val;
        } else {
            diff = Math.min(diff, root.val - prev);
            prev = root.val;
        }

        helper(root.right);
    }
}