给定两个值 k1 和 k2（k1 < k2）和一个二叉查找树的根节点。找到树中所有值在 k1 到 k2 范围内的节点。即打印所有x (k1 <= x <= k2) 其中 x 是二叉查找树的中的节点值。返回所有升序的节点值。

样例

如果有 k1 = 10 和 k2 = 22, 你的程序应该返回 [12, 20, 22].

    20
   /  \
  8   22
 / \
4   12

/**
 * 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
     */
    public List<Integer> searchRange(TreeNode root, int k1, int k2) {
       // write your code here
		List<Integer> list = new ArrayList<>();
		inOrderRec(root, list, k1, k2);
		return list;
    }
	
	public void inOrderRec(TreeNode root, List<Integer> list, int k1, int k2){  
        if(root!=null){  
        	inOrderRec(root.left, list, k1, k2);  
            if (root.val >= k1 && root.val <= k2) {
				list.add(root.val);
			}
            else if (root.val> k2) {
				return;
			}
            inOrderRec(root.right, list, k1, k2);  
        }  
    }  
}