{"id":493,"date":"2020-09-26T10:48:19","date_gmt":"2020-09-26T02:48:19","guid":{"rendered":"http:\/\/39.96.58.60\/?p=493"},"modified":"2022-10-18T16:39:03","modified_gmt":"2022-10-18T08:39:03","slug":"leetcode-141-%e7%8e%af%e5%bd%a2%e9%93%be%e8%a1%a8","status":"publish","type":"post","link":"http:\/\/www.yatenglg.cn\/blog\/?p=493","title":{"rendered":"Leetcode 141. \u73af\u5f62\u94fe\u8868"},"content":{"rendered":"<p>\u7ed9\u5b9a\u4e00\u4e2a\u94fe\u8868\uff0c\u5224\u65ad\u94fe\u8868\u4e2d\u662f\u5426\u6709\u73af\u3002<\/p>\n<p>\u5982\u679c\u94fe\u8868\u4e2d\u6709\u67d0\u4e2a\u8282\u70b9\uff0c\u53ef\u4ee5\u901a\u8fc7\u8fde\u7eed\u8ddf\u8e2a <code>next<\/code> \u6307\u9488\u518d\u6b21\u5230\u8fbe\uff0c\u5219\u94fe\u8868\u4e2d\u5b58\u5728\u73af\u3002 \u4e3a\u4e86\u8868\u793a\u7ed9\u5b9a\u94fe\u8868\u4e2d\u7684\u73af\uff0c\u6211\u4eec\u4f7f\u7528\u6574\u6570 <code>pos<\/code> \u6765\u8868\u793a\u94fe\u8868\u5c3e\u8fde\u63a5\u5230\u94fe\u8868\u4e2d\u7684\u4f4d\u7f6e\uff08\u7d22\u5f15\u4ece 0 \u5f00\u59cb\uff09\u3002 \u5982\u679c <code>pos<\/code> \u662f <code>-1<\/code>\uff0c\u5219\u5728\u8be5\u94fe\u8868\u4e2d\u6ca1\u6709\u73af\u3002<strong>\u6ce8\u610f\uff1a<code>pos<\/code> \u4e0d\u4f5c\u4e3a\u53c2\u6570\u8fdb\u884c\u4f20\u9012<\/strong>\uff0c\u4ec5\u4ec5\u662f\u4e3a\u4e86\u6807\u8bc6\u94fe\u8868\u7684\u5b9e\u9645\u60c5\u51b5\u3002<\/p>\n<p>\u5982\u679c\u94fe\u8868\u4e2d\u5b58\u5728\u73af\uff0c\u5219\u8fd4\u56de <code>true<\/code> \u3002 \u5426\u5219\uff0c\u8fd4\u56de <code>false<\/code> \u3002<\/p>\n<p>&nbsp;<\/p>\n<p><strong>\u8fdb\u9636\uff1a<\/strong><\/p>\n<p>\u4f60\u80fd\u7528 <em>O(1)<\/em>\uff08\u5373\uff0c\u5e38\u91cf\uff09\u5185\u5b58\u89e3\u51b3\u6b64\u95ee\u9898\u5417\uff1f<\/p>\n<p>&nbsp;<\/p>\n<p><strong>\u793a\u4f8b 1\uff1a<\/strong><\/p>\n<p><img alt=\"\" src=\"https:\/\/assets.leetcode-cn.com\/aliyun-lc-upload\/uploads\/2018\/12\/07\/circularlinkedlist.png\" style=\"height: 97px; width: 300px;\"><\/p>\n<pre><strong>\u8f93\u5165\uff1a<\/strong>head = [3,2,0,-4], pos = 1\n\n<strong>\u8f93\u51fa\uff1a<\/strong>true\n\n<strong>\u89e3\u91ca\uff1a<\/strong>\u94fe\u8868\u4e2d\u6709\u4e00\u4e2a\u73af\uff0c\u5176\u5c3e\u90e8\u8fde\u63a5\u5230\u7b2c\u4e8c\u4e2a\u8282\u70b9\u3002\n\n<\/pre>\n<p><strong>\u793a\u4f8b&nbsp;2\uff1a<\/strong><\/p>\n<p><img alt=\"\" src=\"https:\/\/assets.leetcode-cn.com\/aliyun-lc-upload\/uploads\/2018\/12\/07\/circularlinkedlist_test2.png\" style=\"height: 74px; width: 141px;\"><\/p>\n<pre><strong>\u8f93\u5165\uff1a<\/strong>head = [1,2], pos = 0\n\n<strong>\u8f93\u51fa\uff1a<\/strong>true\n\n<strong>\u89e3\u91ca\uff1a<\/strong>\u94fe\u8868\u4e2d\u6709\u4e00\u4e2a\u73af\uff0c\u5176\u5c3e\u90e8\u8fde\u63a5\u5230\u7b2c\u4e00\u4e2a\u8282\u70b9\u3002\n\n<\/pre>\n<p><strong>\u793a\u4f8b 3\uff1a<\/strong><\/p>\n<p><img alt=\"\" src=\"https:\/\/assets.leetcode-cn.com\/aliyun-lc-upload\/uploads\/2018\/12\/07\/circularlinkedlist_test3.png\" style=\"height: 45px; width: 45px;\"><\/p>\n<pre><strong>\u8f93\u5165\uff1a<\/strong>head = [1], pos = -1\n\n<strong>\u8f93\u51fa\uff1a<\/strong>false\n\n<strong>\u89e3\u91ca\uff1a<\/strong>\u94fe\u8868\u4e2d\u6ca1\u6709\u73af\u3002\n\n<\/pre>\n<p>&nbsp;<\/p>\n<p><strong>\u63d0\u793a\uff1a<\/strong><\/p>\n<ul>\n<li>\u94fe\u8868\u4e2d\u8282\u70b9\u7684\u6570\u76ee\u8303\u56f4\u662f <code>[0, 10<sup>4<\/sup>]<\/code><\/li>\n<li><code>-10<sup>5<\/sup> &lt;= Node.val &lt;= 10<sup>5<\/sup><\/code><\/li>\n<li><code>pos<\/code> \u4e3a <code>-1<\/code> \u6216\u8005\u94fe\u8868\u4e2d\u7684\u4e00\u4e2a <strong>\u6709\u6548\u7d22\u5f15<\/strong> \u3002<\/li>\n<\/ul>\n<p>**\u96be\u5ea6**: Easy<\/p>\n<p>**\u6807\u7b7e**: \u94fe\u8868\u3001 \u53cc\u6307\u9488\u3001<\/p>\n<div class=\"hcb_wrap\">\n<pre class=\"prism undefined-numbers lang-python\" data-lang=\"Python\"><code>\n# -*- coding: utf-8 -*-\n# @Author  : LG\n\n\"\"\"\n\u6267\u884c\u7528\u65f6\uff1a52 ms, \u5728\u6240\u6709 Python3 \u63d0\u4ea4\u4e2d\u51fb\u8d25\u4e8696.73% \u7684\u7528\u6237\n\u5185\u5b58\u6d88\u8017\uff1a16.4 MB, \u5728\u6240\u6709 Python3 \u63d0\u4ea4\u4e2d\u51fb\u8d25\u4e8623.93% \u7684\u7528\u6237\n\n\u89e3\u9898\u601d\u8def\uff1a\n    \u5feb\u6162\u6307\u9488\n    \u82e5\u5b58\u5728\u73af\uff0c\u5feb\u6307\u9488\u4f1a\u5148\u5165\u73af\uff0c\u6162\u6307\u9488\u540e\u5982\u73af\u3002\u5728\u73af\u4e2d\uff0c\u5feb\u6162\u6307\u9488\u76f8\u9047\uff0c\u8fd4\u56deTrue\n    \u82e5\u4e0d\u5b58\u5728\u73af\uff0c\u5feb\u6307\u9488\u5148\u5230\u8fbe\u94fe\u8868\u672b\u5c3e\n\"\"\"\nclass Solution:\n    def hasCycle(self, head: ListNode) -&gt; bool:\n        l, f = ListNode(0, next=head), head # \u6162\u6307\u9488\uff0c\u5feb\u6307\u9488\n        while l != f:   # \u5feb\u6162\u6307\u9488\u4e0d\u540c\uff0c\u5faa\u73af\n            if f and f.next:\n                l = l.next  # \u6162\u6307\u9488\u8d70\u4e00\u6b65\n                f = f.next.next # \u5feb\u6307\u9488\u8d70\u4e24\u6b65\n            else:\n                return False    # \u82e5\u8fbe\u5230\u94fe\u8868\u672b\u5c3e\uff0c\u5219\u65e0\u73af\n        return True<\/code><\/pre>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u7ed9\u5b9a\u4e00\u4e2a\u94fe\u8868\uff0c\u5224\u65ad\u94fe\u8868\u4e2d\u662f\u5426\u6709\u73af\u3002 \u5982\u679c\u94fe\u8868\u4e2d\u6709\u67d0\u4e2a\u8282\u70b9\uff0c\u53ef\u4ee5\u901a\u8fc7\u8fde\u7eed\u8ddf\u8e2a next \u6307\u9488\u518d\u6b21\u5230\u8fbe\uff0c\u5219\u94fe\u8868\u4e2d\u5b58&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":[],"categories":[11,1],"tags":[],"_links":{"self":[{"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/posts\/493"}],"collection":[{"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=493"}],"version-history":[{"count":1,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/posts\/493\/revisions"}],"predecessor-version":[{"id":494,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=\/wp\/v2\/posts\/493\/revisions\/494"}],"wp:attachment":[{"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=493"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=493"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.yatenglg.cn\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=493"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}