题目:Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST
给一个递增的链表,转化成高度平衡的二叉查找树。
先遍历一边算出链表的个数,在递归求解。
注意就是左右字数划分的范围,还有右子树的头指针需要求出。
/**
* 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) {
int n=0;
ListNode *p=head;
while(p!=NULL)n++,p=p->next;
return build(head,n);
}
TreeNode *build(ListNode *head,int n)
{
if(head==NULL||n==0)return NULL;
ListNode *p=head;
for(int i=1;i<(n+1)/2;++i)p=p->next;
TreeNode *root=new TreeNode(p->val);
root->left=build(head,(n+1)/2-1);
root->right=build(p->next,n-(n+1)/2);
}
};