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The task is simple: given any positive integer N, you are supposed to count the total number of 1's in the decimal form of the integers from 1 to N. F 阅读全文
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Given two strings S1 and S2, S=S1−S2 is defined to be the remaining string after taking all the characters in S2 from S1. Your task 阅读全文
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Given a stack which can keep M numbers at most. Push N numbers in the order of 1, 2, 3, ..., N and pop randomly. You are supposed to tell if a given s 阅读全文
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A linked list consists of a series of structures, which are not necessarily adjacent in memory. We assume that each structure contains an integer key 阅读全文