LeetCode Convert Sorted List to Binary Search Tree

最新推荐文章于 2022-02-19 22:56:38 发布

原创最新推荐文章于 2022-02-19 22:56:38 发布 · 633 阅读

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本文介绍了一种将有序链表转换为高度平衡的二叉搜索树(BST)的方法。通过递归地选择中间节点作为根节点来确保树的高度平衡，并保持BST的性质。文章提供了一个C++实现示例。

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Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

把有序链表转换为二叉查找树

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:

    TreeNode *listToBST(ListNode *&head, int first, int last) {
        if (first > last)
            return NULL;
        int mid = (first+last)/2;
        TreeNode *node = new TreeNode(-1);
        node->left = listToBST(head, first, mid-1);
        node->val = head->val;
        head = head->next;
        node->right = listToBST(head, mid+1, last);
        return node;
    }
    TreeNode *sortedListToBST(ListNode *head) {
        if (head==NULL)
            return NULL;
        int length = 0;
        ListNode *tmp = head;
        while (head!=NULL) {
            length++;
            head = head->next;
        }
        return listToBST(tmp, 0, length-1);
    }
};