数论

GCD （ 辗转相除法

#include<iostream>
using namespace std;
int gcd(int a,int b)
{
	while(b!=0)
	{
		int r = b;
		b %= a;
		a = r;
	}
	return a;
}
/*int gcd(int a,int b)
{
return b ? gcd(b,a%b):a;
}
*/
int main()
{
	int a,b;
	cin>>a>>b; 
	cout<<gcd(a,b)<<endl;// a < b 
	return 0;
} 

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