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  • 106. 排序列表转换为二分查找树

    106. 排序列表转换为二分查找树 

     

    给出一个所有元素以升序排序的单链表,将它转换成一棵高度平衡的二分查找树

    样例
                   2
    1->2->3  =>   / 
                 1   3
    
    标签 
     
    /**
     * Definition of ListNode
     * class ListNode {
     * public:
     *     int val;
     *     ListNode *next;
     *     ListNode(int val) {
     *         this->val = val;
     *         this->next = NULL;
     *     }
     * }
     * Definition of TreeNode:
     * class TreeNode {
     * public:
     *     int val;
     *     TreeNode *left, *right;
     *     TreeNode(int val) {
     *         this->val = val;
     *         this->left = this->right = NULL;
     *     }
     * }
     */
    
    
    class Solution {
    public:
           /**
         * @param head: The first node of linked list.
         * @return: a tree node
         */
        TreeNode *sortedListToBST(ListNode *head) {
            // write your code here
         	//用递归 
        	TreeNode* root = nullptr;
        	if (head != nullptr)
        	{
        		ListNode *left = nullptr, *right = nullptr;
        		root = new TreeNode(dichotomyList(head, left, right));
        		root->left = sortedListToBST(left);
        		root->right = sortedListToBST(right);
        	}
        }
    
        int dichotomyList(ListNode *head, ListNode *&left, ListNode *&right) {
           	if (head->next != nullptr)
        	{
        		ListNode *fast = head, *slow = head, *temp = head;
        		while (fast != nullptr && fast->next != nullptr)
        		{
        			temp = slow;
        			slow = slow->next;
        			fast = fast->next->next;
        		}
        		temp->next = nullptr;
        		left = head;
        		right = slow->next;
        		return slow->val;
        	}
        	else
        	{
        		left = nullptr;
        		right = nullptr;
        		return head->val;
        	}
        }
    };
    

      

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  • 原文地址:https://www.cnblogs.com/kanekiken/p/8040545.html
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