摘要：Description: Count the number of prime numbers less than a non-negative number, n. 阅读全文

摘要：Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longes 阅读全文

摘要：Given a string, find the length of the longest substring without repeating characters. Examples: Given "abcabcbb", the answer is "abc", which the leng 阅读全文