摘要： We say that integer x, 0 x p, is a primitive root modulo odd prime p if and only if the set { (xi mod p) | 1 = i = p-1 } is equal to { 1, ..., p-1 }. For example, the consecutive powers of 3 modulo 7 are 3, 2, 6, 4, 5, 1, and thus 3 is a primitive root modulo 7. Write a program which given any odd prime 3 = p 65536 outputs the number of primitive roots modulo p. 阅读全文

摘要： 欧几里德算法又称辗转相除法，用于计算两个整数a,b的最大公约数。其计算原理依赖于下面的定理： 　　gcd函数就是用来求(a,b)的最大公约数的。 　　gcd函数的基本性质： 　　gcd(a,b)=gcd(b,a)=gcd(-a,b)=gcd(|a|,|b|) 阅读全文

摘要： In how many ways can you tile a 2xn rectangle by 2x1 or 2x2 tiles? Here is a sample tiling of a 2x17 rectangle. 阅读全文