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  • [Linked List]Convert Sorted List to Binary Search Tree

    Total Accepted: 57775 Total Submissions: 198972 Difficulty: Medium

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

     
    /**
     * 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:
        int getListNodeLength(ListNode* head)
        {
            int len = 0;
            while(head){
                len++;
                head = head->next;
            }
            return len;
        }
        TreeNode* sortedListToBST(ListNode* head) {
            if(head==NULL){
                return NULL;
            }
            if(head->next==NULL){
                return new TreeNode(head->val);
            }
            int len = getListNodeLength(head);
            int cnt = len/2;
         
            ListNode* cur      = head;
            while(--cnt){
                cur = cur->next;
            }
            ListNode* mid  = cur->next;
            ListNode* head2= mid->next;
            cur->next      = NULL;
            mid->next      = NULL;
    
            
            TreeNode* root = new TreeNode(mid->val);
            root->left     = sortedListToBST(head);
            root->right    = sortedListToBST(head2);
            return root;
        }
    };
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  • 原文地址:https://www.cnblogs.com/zengzy/p/5041814.html
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