[exgcd算最值] luogu 3951

题目

代码

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
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#if __cplusplus >= 201103L
#include 
#include 
#endif
#define int long long
using namespace std;
const int INF = 0x3f3f3f3f;
int x,y;
void exgcd(int a,int b){
	if(b==0){
		x=1;
		y=0;
		return;
	}
	exgcd(b,a%b);
	int tmp=x;
	x=y;
	y=tmp-(a/b)*y;
}
signed main(){
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	int a,b;
	cin>>a>>b;
	exgcd(a,b); 
	int tmp=(-x)/b;
	x+=tmp*b;
	y-=tmp*y;
	while(x<0){
		x+=b;
		y-=a;
	}
	int xx=x;
	while(x>0){
		x-=b;
		y+=a;
	}
	int yy=y;
	//cout<
	cout<<a*(xx-1)+b*(yy-1)-1<<endl;
    return 0;
}