141.环形链表.go

/*
 * @lc app=leetcode.cn id=141 lang=golang
 *
 * [141] 环形链表
 */

// @lc code=start
/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */

package main

import "fmt"

type ListNode struct {
	Val  int
	Next *ListNode
}

func hasCycle(head *ListNode) bool {
	p1 := head
	p2 := head

	for p2.Next != nil && p2.Next.Next != nil {
		p1 = p1.Next
		p2 = p2.Next.Next

		if p2 == nil {
			return false
		}

		if p1.Val == p2.Val {
			return true
		}
	}

	return false
}

func main() {
	var result bool

	v1 := &ListNode{0, nil}
	v2 := &ListNode{1, nil}

	v1.Next = nil
	result = hasCycle(v1)
	fmt.Printf("one node is %t\n", result)

	v1.Next = v2
	result = hasCycle(v1)
	fmt.Printf("two node is %t\n", result)

	fmt.Println("v2")
	v21 := &ListNode{0, nil}
	v21.Next = v21
	result = hasCycle(v21)
	fmt.Printf("one circle node is %t\n", result)

	fmt.Println("v3")
	v31 := &ListNode{0, nil}
	v32 := &ListNode{0, nil}
	v31.Next = v32
	v32.Next = v31
	result = hasCycle(v31)
	fmt.Printf("two circle node is %t\n", result)

}

// @lc code=end