11. 二叉查找树中搜索区间

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11. 二叉查找树中搜索区间

给定一个二叉查找树和范围[k1, k2]。按照升序返回给定范围内的节点值。

样例

样例 1:

输入：{5},6,10

输出：[]

5

它将被序列化为 {5}

没有数字介于6和10之间

样例 2:

输入：{20,8,22,4,12},10,22

输出：[12,20,22]

解释：

20

/ \

8 22

/ \

4 12

它将被序列化为 {20,8,22,4,12}

[12,20,22]介于10和22之间

/**
* 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
     */
    public List<Integer> searchRange(TreeNode root, int k1, int k2) {
        // write your code here
           List<Integer> ret=new ArrayList<>();
            preSerialization(root , ret,  k1,  k2);
            return  ret;
        }

        public void preSerialization(TreeNode treeNode ,List<Integer> ret, int k1, int k2){
            if(treeNode != null){
                if (k1<=treeNode.val&&treeNode.val<=k2){
                    ret.add(treeNode.val);
                }
                preSerialization(treeNode.left, ret,  k1,  k2);
                preSerialization(treeNode.right, ret,  k1,  k2);
            }
        }
}