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:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */

class Solution {
public:
    /**
     * @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
     */
     
    vector<int> ret;
    vector<int> searchRange(TreeNode * root, int k1, int k2) 
    {
        // write your code here
        if(root  != NULL)
        {
            if(root->val >= k1 && root->val <= k2)
                ret.push_back(root->val);
            //return ret;
            searchRange(root->left, k1, k2);
            searchRange(root->right, k1, k2);
            
        }
        return ret;
        
    }
};