LeetCode:Rotate List
Rotate List
Total Accepted: 66597 Total
Submissions: 291807 Difficulty: Medium
Given a list, rotate the list to the right by k places, where k is non-negative.
For example:
Given 1->2->3->4->5->NULL
and k = 2
,
return 4->5->1->2->3->NULL
.
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思路:
1.如给出的样例。找到指向3的指针(p)和指向5的指针(q);
2.将5指向1变成一个环(q->next = head);
3.将4变成新头(head = p->next);
4.将3指向空(p = NULL)。
关键是要求:p、q指针。能够用快、慢指针求,可是因为k可能 > 链表的长度,
因此直接求链表的长度比較方便你。
code:
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNode* rotateRight(ListNode* head, int k) { ListNode *p = head; ListNode *q = head; if(!q || !k) return head; // 求出链表长度 int len = 1; while(q->next){ len++; q = q->next; } q->next = p; // 变成一个环 k %= len; k = len - k; while(--k) p = p->next; // 找到新头结点的前一个结点 head = p->next; p->next = NULL; return head; } };
posted on 2017-08-13 11:44 cynchanpin 阅读(159) 评论(0) 编辑 收藏 举报