Problem:
Given a linked list, swap every two adjacent nodes and return its head.
For example,
Given 1->2->3->4
, you should return the list as 2->1->4->3
.
Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
Solution:
单纯的链表指针操作,没有什么好讲的,复杂度O(n)
题目大意:
给一个链表,要求将链表的奇数个节点和它后边的节点进行互换,并且不能更改节点的值(也就是不能互换节点的值),空间复杂度要求为O(1)
Java源代码(272ms):
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ public class Solution { public ListNode swapPairs(ListNode head) { ListNode p=new ListNode(0),s; p.next=head; head=p; while(p.next!=null && p.next.next!=null){ s=p.next.next; p.next.next=s.next; s.next=p.next; p.next=s; p=s.next; } return head.next; } }
C语言源代码(1ms)不开辟新的节点内存:
/** * Definition for singly-linked list. * struct ListNode { * int val; * struct ListNode *next; * }; */ struct ListNode* swapPairs(struct ListNode* head) { struct ListNode *p=head,*s; if(p!=NULL && p->next!=NULL){ s=p->next; p->next=s->next; s->next=p; head=s; while(p->next!=NULL && p->next->next!=NULL){ s=p->next->next; p->next->next=s->next; s->next=p->next; p->next=s; p=s->next; } } return head; }
C++源代码(9ms):
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNode* swapPairs(ListNode* head) { ListNode *p,*s; p=new ListNode(0); p->next=head; head=p; while(p->next!=NULL && p->next->next!=NULL){ s=p->next->next; p->next->next=s->next; s->next=p->next; p->next=s; p=s->next; } return head->next; } };
Python源代码(81ms):
# Definition for singly-linked list. # class ListNode: # def __init__(self, x): # self.val = x # self.next = None class Solution: # @param {ListNode} head # @return {ListNode} def swapPairs(self, head): p=ListNode(0) p.next=head;head=p while p.next!=None and p.next.next!=None: s=p.next.next p.next.next=s.next s.next=p.next p.next=s p=s.next return head.next
时间: 2024-08-11 01:35:33