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摘要： 描述Given a string of symbols, it’s natural to look it over and see what substrings are present. In this problem, you are given a string and asked to consider what substrings are absent. Of course, a given string has finite length and therefore only finitely many substrings, so there are always infini 阅读全文

摘要： 描述How can millions of different and complex structures be built using only a few simple building blocks? Just ask your DNA. DNA (short for deoxyribonucleic acid) spells out the genetic codes of millions of species, using just four molecules: adenine (A), guanine (G), thymine (T), and cytosine (C). T 阅读全文