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CLK/NumberTheory/Factors.hpp
2018-05-13 15:19:52 -04:00

51 lines
893 B
C++

//
// Factors.hpp
// Clock Signal
//
// Created by Thomas Harte on 29/07/2016.
// Copyright 2016 Thomas Harte. All rights reserved.
//
#ifndef Factors_hpp
#define Factors_hpp
#include <numeric>
#include <utility>
namespace NumberTheory {
/*!
@returns The greatest common divisor of @c a and @c b.
*/
template<class T> T greatest_common_divisor(T a, T b) {
#if __cplusplus > 201402L
return std::gcd(a, b);
#else
if(a < b) {
std::swap(a, b);
}
while(1) {
if(!a) return b;
if(!b) return a;
T remainder = a%b;
a = b;
b = remainder;
}
#endif
}
/*!
@returns The least common multiple of @c a and @c b computed indirectly via the greatest
common divisor.
*/
template<class T> T least_common_multiple(T a, T b) {
if(a == b) return a;
T gcd = greatest_common_divisor<T>(a, b);
return (a / gcd) * (b / gcd) * gcd;
}
}
#endif /* Factors_hpp */