lintcode-二叉树中查找区间

/** * Definition of TreeNode: * public class TreeNode { *     public int val; *     public TreeNode left, right; *     public TreeNode(int val) { *         this.val = val; *         this.left = this.right = null; *     } * } */public class Solution {    /*     * @param root: param root: The root of the binary search tree     * @param k1: An integer     * @param k2: An integer     * @return: return: Return all keys that k1<=key<=k2 in ascending order     */     ArrayList<Integer> result = new ArrayList<>();    public List<Integer> searchRange(TreeNode root, int k1, int k2) {        // write your code here        inOrder(root, k1, k2);        return result;    }    private void inOrder(TreeNode root, int k1, int k2) {        if(root == null)return;        inOrder(root.left, k1, k2);        if(root.val <= k2 && root.val >= k1) {            result.add(root.val);        }        inOrder(root.right, k1, k2);    }}