RosettaCodeData/Task/Chinese-remainder-theorem/C++/chinese-remainder-theorem.cpp
2023-07-01 13:44:08 -04:00

53 lines
851 B
C++

// Requires C++17
#include <iostream>
#include <numeric>
#include <vector>
#include <execution>
template<typename _Ty> _Ty mulInv(_Ty a, _Ty b) {
_Ty b0 = b;
_Ty x0 = 0;
_Ty x1 = 1;
if (b == 1) {
return 1;
}
while (a > 1) {
_Ty q = a / b;
_Ty amb = a % b;
a = b;
b = amb;
_Ty xqx = x1 - q * x0;
x1 = x0;
x0 = xqx;
}
if (x1 < 0) {
x1 += b0;
}
return x1;
}
template<typename _Ty> _Ty chineseRemainder(std::vector<_Ty> n, std::vector<_Ty> a) {
_Ty prod = std::reduce(std::execution::seq, n.begin(), n.end(), (_Ty)1, [](_Ty a, _Ty b) { return a * b; });
_Ty sm = 0;
for (int i = 0; i < n.size(); i++) {
_Ty p = prod / n[i];
sm += a[i] * mulInv(p, n[i]) * p;
}
return sm % prod;
}
int main() {
vector<int> n = { 3, 5, 7 };
vector<int> a = { 2, 3, 2 };
cout << chineseRemainder(n,a) << endl;
return 0;
}