530 Minimum Absolute Difference in BST

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

Example:

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).

Note:There are at least two nodes in this BST.

Solution)

Based on inorder traversing, calculate absolute distance between two nodes.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int getMinimumDifference(TreeNode root) {
        Stack<TreeNode> stack = new Stack<>();
        TreeNode node = root;
        TreeNode prev = null;
        int min = Integer.MAX_VALUE;
        while(!stack.isEmpty() || node != null) {
            while(node != null) {
                stack.push(node);
                node = node.left;
            }
            TreeNode temp = stack.pop();
            if (prev != null) {
                min = Math.min(min, Math.abs(temp.val-prev.val));
            }
            prev = temp;
            node = temp.right;
        }
        return min;
    }
}