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Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length. Do not allocate extra space fo 阅读全文
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Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the 阅读全文
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leetcode 阅读全文
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Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Note: Do not modify the linked list. Follow up:Can you 阅读全文
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Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? 题意： 判断一个链表是否有环。 解决方案： 双指针，快指针每次走两步，慢指针每次 阅读全文
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Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library functio 阅读全文
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Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another e 阅读全文