MinimumAbsoluteDifferenceInBST.java

public class MinimumAbsoluteDifferenceInBST {
    long result = Integer.MAX_VALUE;

    public int getMinimumDifference(TreeNode root) {
        computeMinAbsoluteDifference(root, Integer.MIN_VALUE, Integer.MAX_VALUE);
        return (int) result;
    }

    public void computeMinAbsoluteDifference(TreeNode root, long left, long right) {
        if (root == null) return;
        result = Math.min(result, Math.min(root.val - left, right - root.val));
        computeMinAbsoluteDifference(root.left, left, root.val);
        computeMinAbsoluteDifference(root.right, root.val, right);
    }
}