[leetcode]230. Kth Smallest Element in a BST

最新推荐文章于 2023-06-03 15:29:39 发布

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本文介绍了一个解决LeetCode上关于二叉搜索树中寻找第K小元素的问题的方法。通过迭代遍历的方式实现了一个高效的算法，该算法能够有效地找到二叉搜索树中的第K小元素。

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题目链接：https://leetcode.com/problems/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?

class Solution{
public:
    int kthSmallest(TreeNode* root,int k)
    {
        stack<TreeNode*> _stack;
        int i=0;
        TreeNode* p=root;
        while(p!=NULL||!_stack.empty())
        {
            while(p!=NULL)
            {
                _stack.push(p);
                p=p->left;
            }
            if(!_stack.empty())
            {
                p=_stack.top();
                _stack.pop();
                i++;
                if(i==k)
                    return p->val;
                p=p->right;
            }
        }
        return p->val;
    }
};