【题目】
Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.
【题意】
将一个有序链表转换成平衡二叉树
【思路】
思路跟Convert Sorted Array to Binary Search Tree完全一样
【代码】
/** * 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: ListNode *getMidNode(ListNode *head){ if(head==NULL || head->next==NULL)return head; ListNode* prev=NULL; //指向pstep1的前一个节点 ListNode* pstep1=head; //每次向前移动一步 ListNode* pstep2=head->next; //每次向前移动两步 //对于偶数链表,结束条件是pstep2->next==NULL //对于计数链表,结束条件是pstep2==NULL while(pstep2!=NULL && pstep2->next!=NULL){ prev=pstep1; pstep1=pstep1->next; pstep2=pstep2->next->next; } //找到链表中间节点的同时,把链表分裂为前后两个独立的链表 if(prev)prev->next=NULL; return pstep1; } TreeNode *sortedListToBST(ListNode *head) { if(head==NULL)return NULL; ListNode*mid=getMidNode(head); //创建根节点 TreeNode*root=(TreeNode*)malloc(sizeof(TreeNode)); root->val=mid->val; //创建左子树 TreeNode*left=NULL; if(mid!=head) left=sortedListToBST(head); //创建右子树 TreeNode*right=sortedListToBST(mid->next); //构造二叉树 root->left=left; root->right=right; return root; } };
LeetCode: Convert Sorted List to Binary Search Tree [109]
时间: 2024-10-17 19:38:19