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/*
* SYNOPSIS:
*
* # g++ -o gcd-cpp gcd.cpp
* # ./gcd-cpp 11 22 33 121
* # 11
*
*
* To use GNU Multiple Precision Arithmetic Library:
*
* # g++ -DGMP gcd.cpp -lgmpxx -lgmp -o gcd-cpp-gmp
* # ./gcd-cpp-gmp 1234567890987654321 987654321234567
* # 63
*
*/
#include <cstdlib>
#include <iostream>
#include <sstream>
#include <vector>
#if __cplusplus >= 201703L
#include <execution>
#include <numeric>
#endif
#ifdef GMP
#include <gmpxx.h>
typedef mpz_class Number;
#else
typedef unsigned long Number;
#endif
using std::vector;
template <class N> N gcd2(N a, N b) {
while (b != 0) {
N c = b;
b = a % b;
a = c;
}
return a;
}
#if __cplusplus >= 201703L
template <class N> class GCD {
public:
N operator()(N a, N b) const { return gcd2(a, b); };
};
template <class N> N gcd(const vector<N> &ns) {
GCD<N> GCD;
return reduce(std::execution::par, begin(ns), end(ns), N(0), GCD);
}
#else
template <class N> N gcd(const vector<N> &ns) {
N r = 0;
for (typename vector<N>::const_iterator n = ns.begin(); n != ns.end(); ++n)
r = gcd2(*n, r);
return r;
}
#endif
int main(int argc, char *argv[]) {
if (argc > 1) {
vector<Number> ns(argc - 1);
for (int n = 1; n < argc; ++n) {
std::stringstream str;
str << argv[n];
str >> ns[n - 1];
}
std::cout << gcd(ns) << std::endl;
}
return EXIT_SUCCESS;
}
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