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题目：Given an array of integers, every element appears twice except for one. Find that single one.Note:Your algorithm should have a linear runtime comp... 阅读全文
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题目：Given an unsorted array of integers, find the length of the longest consecutive elements sequence.For example,Given [100, 4, 200, 1, 3, 2],The lon... 阅读全文
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题目：Given a 2D board containing 'X' and 'O', capture all regions surrounded by 'X'.A region is captured by flipping all 'O's into 'X's in that surroun... 阅读全文
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题目：Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are +, -, *, /. Each operand may be an integer or anothe... 阅读全文
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String 字符串常量StringBuffer 字符串变量（线程安全）StringBuilder 字符串变量（非线程安全）简要的说， String 类型和 StringBuffer 类型的主要性能区别其实在于 String 是不可变的对象, 因此在每次对 String 类型进行改变的时候其实都等同... 阅读全文
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题目：Given an absolute path for a file (Unix-style), simplify it.For example,path = "/home/", => "/home"path = "/a/./b/../../c/", => "/c"Corner Cases:D... 阅读全文
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题目：Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.For "(()", the... 阅读全文
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题目：Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.题解：这道题可以应用之前解过的Largetst Recta... 阅读全文
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题目：Given n non-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the ... 阅读全文
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题目：Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.The brackets must close in t... 阅读全文
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题目：Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.get(key) - Get ... 阅读全文
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题目：Sort a linked list in O(n log n) time using constant space complexity.题解：考虑到要求用O(nlogn)的时间复杂度和constant space complexity来sort list，自然而然想到了merge sor... 阅读全文
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题目：Given a singly linked list L: L0→L1→…→Ln-1→Ln,reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…You must do this in-place without altering the nodes' values.F... 阅读全文
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leetcode很多题目都是利用快慢指针来解决题目，下面具体讲解下快慢指针。概念： 快指针在每一步走的步长要比慢指针一步走的步长要多。快指针通常的步速是慢指针的2倍。在循环中的指针移动通常为：faster = faster.next.next, slower = slower.next.应用：1.... 阅读全文
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题目：Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.题解：Merge k sorted linked list就是merge 2 sorted li... 阅读全文