Golang 数据结构练习——单链表找环

问题:一个单向链表,怎样怎么检测是否有环,环的初始节点是什么?

package main
import (
 "fmt"
)
type ListNode struct {
 value int
 next *ListNode
}
func NewListNode(i int) *ListNode {
 val := new(ListNode)
 val.value = i
 return val
}
func main() {
 a1 := NewListNode(1)
 a2 := NewListNode(2)
 a3 := NewListNode(3)
 a4 := NewListNode(4)
 a5 := NewListNode(5)
 // 1→2→3→4→5
 // ↑⎽⎽⎽⌟ 
 a1.next = a2
 a2.next = a3
 a3.next = a4
 a4.next = a5
 a5.next = a3
 head := DetectCycle(a1)
 fmt.Println(head.value)
}
func DetectCycle(head *ListNode) *ListNode {
 fast := head
 slow := head
 for {
 if fast.next == nil || slow.next == nil {
 break
 }
 fast = fast.next.next
 slow = slow.next
 if fast == slow {
 // 找到快慢指针相遇点
 break
 }
 }
 if fast == nil || slow == nil {
 return nil
 }
 // 找到快慢指针相遇点后,快慢指针一样的速度移动,找到环的起点
 slow = head
 for {
 if fast == slow {
 break
 }
 fast = fast.next
 slow = slow.next
 }
 return slow
}

本文来自:简书

感谢作者:redexpress

查看原文:Golang 数据结构练习——单链表找环

• 编辑
• 预览