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Problem Description There are many students in PHT School. One day, the headmaster whose name is PigHeader wanted all students stand in a lin... 阅读全文
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Problem Description A Fibonacci sequence is calculated by adding the previous two members the sequence, with the first two members being both... 阅读全文
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Problem Description The “Harry Potter and the Goblet of Fire” will be on show in the next few days. As a crazy fan of Harry Potter, you will ... 阅读全文
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Catalan number,卡特兰数又称卡塔兰数,是组合数学中一个常出现在各种计数问题中出现的数列。以比利时的数学家欧仁·查理·卡塔兰 (1814–1894)命名。卡特兰数的前几个数 前20项为(OEIS中的数列A000108):1, 1, 2, 5, 14, 42, 132, ... 阅读全文