comments | difficulty | edit_url | rating | source | tags | ||
---|---|---|---|---|---|---|---|
true |
中等 |
1386 |
第 223 场周赛 Q2 |
|
给你链表的头节点 head
和一个整数 k
。
交换 链表正数第 k
个节点和倒数第 k
个节点的值后,返回链表的头节点(链表 从 1 开始索引)。
示例 1:
输入:head = [1,2,3,4,5], k = 2 输出:[1,4,3,2,5]
示例 2:
输入:head = [7,9,6,6,7,8,3,0,9,5], k = 5 输出:[7,9,6,6,8,7,3,0,9,5]
示例 3:
输入:head = [1], k = 1 输出:[1]
示例 4:
输入:head = [1,2], k = 1 输出:[2,1]
示例 5:
输入:head = [1,2,3], k = 2 输出:[1,2,3]
提示:
- 链表中节点的数目是
n
1 <= k <= n <= 105
0 <= Node.val <= 100
我们可以先用快指针
时间复杂度
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution:
def swapNodes(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
fast = slow = head
for _ in range(k - 1):
fast = fast.next
p = fast
while fast.next:
fast, slow = fast.next, slow.next
q = slow
p.val, q.val = q.val, p.val
return head
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode() {}
* ListNode(int val) { this.val = val; }
* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
public ListNode swapNodes(ListNode head, int k) {
ListNode fast = head;
while (--k > 0) {
fast = fast.next;
}
ListNode p = fast;
ListNode slow = head;
while (fast.next != null) {
fast = fast.next;
slow = slow.next;
}
ListNode q = slow;
int t = p.val;
p.val = q.val;
q.val = t;
return head;
}
}
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* swapNodes(ListNode* head, int k) {
ListNode* fast = head;
while (--k) {
fast = fast->next;
}
ListNode* slow = head;
ListNode* p = fast;
while (fast->next) {
fast = fast->next;
slow = slow->next;
}
ListNode* q = slow;
swap(p->val, q->val);
return head;
}
};
/**
* Definition for singly-linked list.
* type ListNode struct {
* Val int
* Next *ListNode
* }
*/
func swapNodes(head *ListNode, k int) *ListNode {
fast := head
for ; k > 1; k-- {
fast = fast.Next
}
p := fast
slow := head
for fast.Next != nil {
fast, slow = fast.Next, slow.Next
}
q := slow
p.Val, q.Val = q.Val, p.Val
return head
}
/**
* Definition for singly-linked list.
* class ListNode {
* val: number
* next: ListNode | null
* constructor(val?: number, next?: ListNode | null) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
* }
*/
function swapNodes(head: ListNode | null, k: number): ListNode | null {
let [fast, slow] = [head, head];
while (--k) {
fast = fast.next;
}
const p = fast;
while (fast.next) {
fast = fast.next;
slow = slow.next;
}
const q = slow;
[p.val, q.val] = [q.val, p.val];
return head;
}
/**
* Definition for singly-linked list.
* public class ListNode {
* public int val;
* public ListNode next;
* public ListNode(int val=0, ListNode next=null) {
* this.val = val;
* this.next = next;
* }
* }
*/
public class Solution {
public ListNode SwapNodes(ListNode head, int k) {
ListNode fast = head;
while (--k > 0) {
fast = fast.next;
}
ListNode p = fast;
ListNode slow = head;
while (fast.next != null) {
fast = fast.next;
slow = slow.next;
}
ListNode q = slow;
int t = p.val;
p.val = q.val;
q.val = t;
return head;
}
}