LeetCode - 109. Convert Sorted List to Binary Search Tree

题目

LeetCode - 109. Convert Sorted List to Binary Search Tree

题目链接

https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/

参考博客

解题思路

此题是题108的变体，略过。

解题源码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    
    TreeNode* f(vector<int> &h, int i, int j){
        if (i > j) return nullptr;
        int mid = (i+j+1) /2;
        TreeNode *root = new TreeNode(h[mid]);
        root->left = f(h, i, mid - 1);
        root->right = f(h, mid + 1, j);
        return root;
    }
    
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return f(nums, 0, nums.size() - 1);
    }
    
    TreeNode* sortedListToBST(ListNode* head) {
        vector<int> nums;
        while(head){
            nums.push_back(head->val);
            head = head->next;
        }
        return sortedArrayToBST(nums);
    }
};