Leetcode230 Kth Smallest Element in a BST

最新推荐文章于 2023-06-03 15:29:39 发布

walter1990

最新推荐文章于 2023-06-03 15:29:39 发布

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本文链接：https://blog.youkuaiyun.com/suichen1/article/details/48184883

本文详细介绍了如何使用递归方法在给定的二叉搜索树中找到第K小的元素，包括算法实现和后续优化考虑。

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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?

public class Solution230 {

    public void traverse(TreeNode root, List<Integer> list) {
        if(root == null) return;

        traverse(root.left, list);
        list.add(root.val);
        traverse(root.right,list);
    }

    public int kthSmallest(TreeNode root, int k) {
        int ans = 0;
        List<Integer> list = new ArrayList<Integer>();
        traverse(root,list);
        ans = list.get(k-1);
        return ans;
    }
    public static void main(String[] args) {
        List<Integer> list = new ArrayList<Integer>();

        TreeNode root = new TreeNode(5);
        root.left = new TreeNode(4);
        root.right = new TreeNode(8);

        root.left.left = new TreeNode(2);
        root.left.left.right = new TreeNode(3);
        root.right.left = new TreeNode(6);

        Solution230 result = new Solution230();

    }
}