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A binary watch has 4 LEDs on the top which represent the hours (0 11), and the 6 LEDs on the bottom represent the minutes (0 59). Each LED represents 阅读全文
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Given a string s and a string t, check if s is subsequence of t. You may assume that there is only lower case English letters in both s and t. t is po 阅读全文
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Given two strings s and t which consist of only lowercase letters. String t is generated by random shuffling string s and then add one more letter at 阅读全文
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Given a string, find the first non repeating character in it and return it’s index. If it doesn’t exist, return 1. Examples: Note: You may assume the 阅读全文
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Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the rans 阅读全文
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You are given a list of non negative integers, a1, a2, …, an, and a target, S. Now you have 2 symbols + and . For each integer, you should choose one 阅读全文
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Given an integer array with all positive numbers and no duplicates, find the number of possible combinations that add up to a positive integer target. 阅读全文
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A sequence of numbers is called a wiggle sequence if the differences between successive numbers strictly alternate between positive and negative. The 阅读全文
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We are playing the Guess Game. The game is as follows: I pick a number from 1 to n. You have to guess which number I picked. Every time you guess wron 阅读全文
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Calculate the sum of two integers a and b, but you are not allowed to use the operator + and . Example: Given a = 1 and b = 2, return 3. 阅读全文