題目描述:
給定一個鏈表,兩兩交換其中相鄰的節點,並返回交換後的鏈表。你不能只是單純的改變節點內部的值,而是需要實際的進行節點交換。
示例:
給定 1->2->3->4, 你應該返回 2->1->4->3.
解題思路1:
每次做完一對之後,讓p指向當前a的位置
C++寫法:
代碼:
/**
* 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) {
auto dummy = new ListNode(-1);
dummy -> next = head;
for(auto p = dummy; p -> next && p -> next -> next;)
{
auto a = p -> next, b = a -> next;
p -> next = b;
a -> next = b -> next;
b -> next = a;
p = a;
}
return dummy -> next;
}
};
python寫法:
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution(object):
def swapPairs(self, head):
dummy = ListNode(-1)
dummy.next = head
p = dummy
while p.next and p.next.next:
a = p.next
b = a.next
p.next = b
a.next = b.next
b.next = a
p = a
return dummy.next
題目來源: