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Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.Note: The solution set must not contain dupli... 阅读全文
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Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.分析从前往后扫描，因为左减数字只能最多一位，并且比当前数字小，所以扫描的时候不断判断当前罗马字符和上一个的大小，如果s[i-1] 0 && map(s[i]) > map(s[i - 1... 阅读全文
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Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.分析罗马数字共有7个，即I（1）、V（5）、X（10）、L（50）、C（100）、D（500）和M（1000）。按照下述的规则可以表示任意正整数。需要注意的是罗马数字中没有“0”，与进位制... 阅读全文
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Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.For example, Given [0,1,0,2,1,0,1,3,2,1,2,1], retu... 阅读全文
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Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two ... 阅读全文
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Implement regular expression matching with support for '.' and '*'.'.' Matches any single character. '*' Matches zero or more of the preceding element. The matching should cover the entire input stri... 阅读全文
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Determine whether an integer is a palindrome. Do this without extra space.Some hints:Could negative integers be palindromes? (ie, -1)If you are thinking of converting the integer to string, note the r... 阅读全文
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Implement atoi to convert a string to an integer.Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.... 阅读全文
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Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321click to show spoilers.Have you thought about this?Here are some good questions to ask before coding. Bonus poi... 阅读全文
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The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)P A H N A P L S I I G ... 阅读全文