您的位置：首页 > 其它

LeetCode 230. Kth Smallest Element in a BST

2017-02-13 17:20 267 查看
230. Kth Smallest Element in a BST
Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.

Note: 
You may assume k is always valid, 1 ≤ k ≤ BST's total elements.

Follow up:
What if the BST is modified (insert/delete operations) often and you need to find the kth smallest frequently? How would you optimize the kthSmallest routine?

Hint:

Try to utilize the property of a BST.
What if you could modify the BST node's structure?
The optimal runtime complexity is O(height of BST).

题目大意：给一个二叉搜索树，返回它的第k小的数～
分析：二叉搜索树的中序遍历是从小到大排序的，将前k个遍历结果放入nums中，当nums.size() >= k的时候返回nums[k-1]～
class Solution {
public:
vector<int> nums;
int kthSmallest(TreeNode* root, int k) {
if (root == NULL || nums.size() >= k) return nums[k - 1];
if (root->left != NULL) kthSmallest(root->left, k);
nums.push_back(root->val);
if (root->right != NULL) kthSmallest(root->right, k);
return nums[k - 1];
}
};
内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理 点击这里给我发消息
标签： 
相关文章推荐
新的分享
章节导航