![](https://img.haomeiwen.com/i6745450/2bc879dd9d6026c4.png)
其实任何一种遍历都可以,只是中序遍历方便于剪枝。
中序遍历:本题涉及到二叉查找树的按序输出,应马上联想到二叉树的中序遍历
/**
* 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> searchRange(TreeNode * root, int k1, int k2) {
// write your code here
vector<int> ans;
if(root == NULL) return ans;
inorder(root, ans, k1, k2);
return ans;
}
private:
void inorder(TreeNode* root, vector<int>& nums,int k1, int k2){
if(root == NULL) return;
inorder(root->left, nums, k1, k2);
if(root->val >= k1 && root->val <= k2){
nums.push_back(root->val);
}
inorder(root->right, nums, k1, k2);
}
};
优化:剪枝
/**
* 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> searchRange(TreeNode * root, int k1, int k2) {
// write your code here
vector<int> ans;
if(root == NULL) return ans;
inorder(root, ans, k1, k2);
return ans;
}
private:
void inorder(TreeNode* root, vector<int>& nums,int k1, int k2){
if(root == NULL) return;
if(root->val >= k1) inorder(root->left, nums, k1, k2);
if(root->val >= k1 && root->val <= k2){
nums.push_back(root->val);
}
if(root->val <= k2) inorder(root->right, nums, k1, k2);
}
};
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