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Letter Combinations of a Phone NumberGiven a digit string, return all possible letter combinations that the number could represent.A mapping of digit ... 阅读全文
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Search Insert PositionGiven a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if ... 阅读全文
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Swap Nodes in PairsGiven a linked list, swap every two adjacent nodes and return its head.For example,Given1->2->3->4, you should return the list as2-... 阅读全文
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Multiply StringsGiven two numbers represented as strings, return multiplication of the numbers as a string.Note: The numbers can be arbitrarily large ... 阅读全文
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Permutation SequenceThe set[1,2,3,…,n]contains a total ofn! unique permutations.By listing and labeling all of the permutations in order,We get the fo... 阅读全文
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Valid SudokuDetermine if a Sudoku is valid, according to:Sudoku Puzzles - The Rules.The Sudoku board could be partially filled, where empty cells are ... 阅读全文
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Count and SayThe count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ...1is read off as"one 1"or11.11is r... 阅读全文
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Decode WaysA message containing letters fromA-Zis being encoded to numbers using the following mapping:'A' -> 1'B' -> 2...'Z' -> 26Given an encoded me... 阅读全文
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Sqrt(x)Implementint sqrt(int x).Compute and return the square root ofx.分析：方案一：遍历0~n， 第一次出现i * i > n，返回 i-1即可。方案二：二分搜索： （1） 当n = 0, 或者 n = 1时，返回 n （2... 阅读全文
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Best Time to Buy and Sell Stock IISay you have an array for which theithelement is the price of a given stock on dayi.Design an algorithm to find the ... 阅读全文