LeetCode-Closest Binary Search Tree Value

Given a non-empty binary search tree and a target value, find the value in the BST that is closest to the target.

Note:

• Given target value is a floating point.
• You are guaranteed to have only one unique value in the BST that is closest to the target.

Analysis:

　　Find the two values before and after the target. Use two integer to record the most recent two values.

Solution:

　　

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public class Pair {
        int val1;
        int val2;

        Pair(int v1, int v2) {
            val1 = v1;
            val2 = v2;
        }
    }

    public boolean closestValueRecur(TreeNode curNode, double target, Pair res) {
        if (curNode == null)
            return false;

        if (closestValueRecur(curNode.left, target, res))
            return true;
        res.val1 = res.val2;
        res.val2 = curNode.val;
        if (res.val1 <= target && res.val2 >= target)
            return true;
        if (closestValueRecur(curNode.right, target, res))
            return true;

        return false;
    }

    public int closestValue(TreeNode root, double target) {
        Pair res = new Pair(Integer.MIN_VALUE, Integer.MIN_VALUE);

        closestValueRecur(root, target, res);

        if (res.val1 == Integer.MIN_VALUE)
            return res.val2;
        if (res.val2 <= target)
            return res.val2;

        if (target - res.val1 < res.val2 - target)
            return res.val1;
        else
            return res.val2;
    }
}