mirror of
https://gitee.com/coder-xiaomo/leetcode-problemset
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161 lines
18 KiB
JSON
161 lines
18 KiB
JSON
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"questionId": "141",
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"title": "Linked List Cycle",
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"content": "<p>Given <code>head</code>, the head of a linked list, determine if the linked list has a cycle in it.</p>\n\n<p>There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the <code>next</code> pointer. Internally, <code>pos</code> is used to denote the index of the node that tail's <code>next</code> pointer is connected to. <strong>Note that <code>pos</code> is not passed as a parameter</strong>.</p>\n\n<p>Return <code>true</code><em> if there is a cycle in the linked list</em>. Otherwise, return <code>false</code>.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2018/12/07/circularlinkedlist.png\" style=\"width: 300px; height: 97px; margin-top: 8px; margin-bottom: 8px;\" />\n<pre>\n<strong>Input:</strong> head = [3,2,0,-4], pos = 1\n<strong>Output:</strong> true\n<strong>Explanation:</strong> There is a cycle in the linked list, where the tail connects to the 1st node (0-indexed).\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2018/12/07/circularlinkedlist_test2.png\" style=\"width: 141px; height: 74px;\" />\n<pre>\n<strong>Input:</strong> head = [1,2], pos = 0\n<strong>Output:</strong> true\n<strong>Explanation:</strong> There is a cycle in the linked list, where the tail connects to the 0th node.\n</pre>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2018/12/07/circularlinkedlist_test3.png\" style=\"width: 45px; height: 45px;\" />\n<pre>\n<strong>Input:</strong> head = [1], pos = -1\n<strong>Output:</strong> false\n<strong>Explanation:</strong> There is no cycle in the linked list.\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li>The number of the nodes in the list is in the range <code>[0, 10<sup>4</sup>]</code>.</li>\n\t<li><code>-10<sup>5</sup> <= Node.val <= 10<sup>5</sup></code></li>\n\t<li><code>pos</code> is <code>-1</code> or a <strong>valid index</strong> in the linked-list.</li>\n</ul>\n\n<p> </p>\n<p><strong>Follow up:</strong> Can you solve it using <code>O(1)</code> (i.e. constant) memory?</p>\n",
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"code": "# Definition for singly-linked list.\n# class ListNode:\n# def __init__(self, x):\n# self.val = x\n# self.next = None\n\nclass Solution:\n def hasCycle(self, head: Optional[ListNode]) -> bool:\n ",
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"code": "/**\n * Definition for singly-linked list.\n * function ListNode(val) {\n * this.val = val;\n * this.next = null;\n * }\n */\n\n/**\n * @param {ListNode} head\n * @return {boolean}\n */\nvar hasCycle = function(head) {\n \n};",
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"code": "/**\n * Definition for singly-linked list.\n * class ListNode {\n * val: number\n * next: ListNode | null\n * constructor(val?: number, next?: ListNode | null) {\n * this.val = (val===undefined ? 0 : val)\n * this.next = (next===undefined ? null : next)\n * }\n * }\n */\n\nfunction hasCycle(head: ListNode | null): boolean {\n \n};",
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"code": "/**\n * Definition for a singly-linked list.\n * class ListNode {\n * public $val = 0;\n * public $next = null;\n * function __construct($val) { $this->val = $val; }\n * }\n */\n\nclass Solution {\n /**\n * @param ListNode $head\n * @return Boolean\n */\n function hasCycle($head) {\n \n }\n}",
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"code": "/**\n * Definition for singly-linked list.\n * public class ListNode {\n * public var val: Int\n * public var next: ListNode?\n * public init(_ val: Int) {\n * self.val = val\n * self.next = nil\n * }\n * }\n */\n\nclass Solution {\n func hasCycle(_ head: ListNode?) -> Bool {\n \n }\n}",
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"code": "/**\n * Example:\n * var li = ListNode(5)\n * var v = li.`val`\n * Definition for singly-linked list.\n * class ListNode(var `val`: Int) {\n * var next: ListNode? = null\n * }\n */\n\nclass Solution {\n fun hasCycle(head: ListNode?): Boolean {\n \n }\n}",
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"code": "/**\n * Definition for singly-linked list.\n * type ListNode struct {\n * Val int\n * Next *ListNode\n * }\n */\nfunc hasCycle(head *ListNode) bool {\n \n}",
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