ClosestBSTValue.java

package com.learning.leet.tree;

/**
 * Created by sargonbenjamin on 7/17/19.
 * https://leetcode.com/problems/closest-binary-search-tree-value/
 */
public class ClosestBSTValue {
    TreeNode minNode = null;
    double minDelta = Double.MAX_VALUE;

    public int closestValue(TreeNode root, double target) {

        helper(root, target);
        return minNode ==null ? 0: minNode.val;

    }

    public void helper(TreeNode curr, double target){
        if(curr==null)return;
        if(curr.val==target){
            minNode = curr;
            return;
        }
        double delta = Math.abs((double)curr.val-target);
        if(delta<minDelta){
            minDelta = delta;
            minNode = curr;
        }
        if(target < curr.val){
            helper(curr.left, target);
        }else{
            helper(curr.right, target);
        }
    }


}