zoukankan      html  css  js  c++  java
  • leetcode141:

    给定一个链表,判断链表中是否有环。

    为了表示给定链表中的环,我们使用整数 pos 来表示链表尾连接到链表中的位置(索引从 0 开始)。 如果 pos 是 -1,则在该链表中没有环。

    示例 1:

    输入:head = [3,2,0,-4], pos = 1
    输出:true
    解释:链表中有一个环,其尾部连接到第二个节点。

    哈希表

    =============================================Python=========================================

    # Definition for singly-linked list.
    # class ListNode:
    #     def __init__(self, x):
    #         self.val = x
    #         self.next = None
    
    class Solution:
        def hasCycle(self, head: ListNode) -> bool:
            s = set()
            if not head:
                return False
            while head:
                if head not in s:
                    s.add(head)
                    head = head.next
                else:
                    return True
            return False

    =========================================Java=======================================

    /**
     * Definition for singly-linked list.
     * class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode(int x) {
     *         val = x;
     *         next = null;
     *     }
     * }
     */
    public class Solution {
        public boolean hasCycle(ListNode head) {
            HashSet<ListNode> s = new HashSet<>();
            if (head == null) {
                return false;
            }
            while (head != null) {
                if (s.contains(head) == false) {
                    s.add(head);
                    head = head.next;
                } else {
                    return true;
                }
            }
            return false;
        }
    }

    =========================================Go==================================

    /**
     * Definition for singly-linked list.
     * type ListNode struct {
     *     Val int
     *     Next *ListNode
     * }
     */
    func hasCycle(head *ListNode) bool {
        m := make(map[*ListNode]int)
        for head != nil {
            if _, ok := m[head]; ok{
                return true
            }
            m[head] = 1
            head = head.Next
        }
        return false
    }

    双指针

    =============================================Python=========================================

    # Definition for singly-linked list.
    # class ListNode:
    #     def __init__(self, x):
    #         self.val = x
    #         self.next = None
    
    class Solution:
        def hasCycle(self, head: ListNode) -> bool:
            fast = slow = head
            if not head:
                return False
            while fast and fast.next:
                fast = fast.next.next
                slow = slow.next
                if slow == fast:
                    return True
            return False
  • 相关阅读:
    C#可视化程序设计第三章(3,4)
    "Can’t be opened because Apple cannot check it for malicious software" 解决方案
    Mac系统.DS_Store文件导致IOError: [Errno 20] Not a directory:解决方案
    读书笔记 《局外人》
    Chrome 67之后无法离线安装插件
    函数和方法的区别
    github|webstorm
    webstorm
    Markdown
    github
  • 原文地址:https://www.cnblogs.com/liushoudong/p/13496845.html
Copyright © 2011-2022 走看看