Convert Sorted List to Binary Search Tree.txt

/**
 * 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 *sortedListToBST(ListNode *head) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> num;
        while (head != NULL) {
            num.push_back(head->val);
            head = head->next;
        }
          if (num.size() == 0)
            return NULL;
        else
            return createNode(num, 0, num.size()-1);
        
    }
    TreeNode* createNode(vector<int>& num, int s, int r) {
        if (s > r)
            return NULL;
        else {
            int p = (s+r)/2;
            TreeNode* node = new TreeNode(num[p]);
            node->left = createNode(num, s, p-1);
            node->right = createNode(num, p+1, r);
            return node;
        }
    }
};