530. Minimum Absolute Difference in BST

2020, Nov 20 One min read

1. Description

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

2. Example

Example 1

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

Example 2

Example 2
Input: root = [1,0,48,null,null,12,49]
Output: 1

3. Constraints

The number of nodes in the tree is in the range [2, $10^4$].
0 <= Node.val <= $10^5$

4. Solutions

Depth-First Search && In-order Traverse

n is the number of nodes in root
Time complexity: O(n)
Space complexity: O(logn->n)

class Solution {
public:
    int getMinimumDifference(TreeNode *root) {
        int prev_value = numeric_limits<int>::max(), min_difference = numeric_limits<int>::max();

        traverse(root, prev_value, min_difference);

        return min_difference;
    }

private:
    void traverse(TreeNode *root, int &prev_value, int &min_difference) {
        if (root == nullptr) {
            return;
        }

        traverse(root->left, prev_value, min_difference);

        if (prev_value < root->val) {
            min_difference = min(root->val - prev_value, min_difference);
        }
        prev_value = root->val;

        traverse(root->right, prev_value, min_difference);
    }
};