Romantic

The Sky is Sprite.
The Birds is Fly in the Sky.
The Wind is Wonderful.
Blew Throw the Trees
Trees are Shaking, Leaves are Falling.
Lovers Walk passing, and so are You. 
................................Write in English class by yifenfei

 

Girls are clever and bright. In HDU every girl like math. Every girl like to solve math problem!
Now tell you two nonnegative integer a and b. Find the nonnegative integer X and integer Y to satisfy X*a + Y*b = 1. If no such answer print "sorry" instead.

#include<cstdio>
#include<iostream>
#define ll long long int  
using namespace std;
ll gcd(ll &x, ll &y, ll a, ll b)
{
	if (b == 0)
	{
		x = 1;
		y = 0;
		return a;
	}
	ll r = gcd(x, y, b, a%b), t;
	t = x;
	x = y;
	y = t - (a / b)*y;
	return r;
}
int main()
{
	ll a, b;
	while (cin >> a >> b)
	{
		ll x, y;
		ll g = gcd(x, y, a, b);
		if (g == 1)
		{
			if (x > 0)
			{
				printf("%lld %lld\n", x, y);
			}
			else
			{
				printf("%lld %lld\n", (x%b + b) % b, (y%a - a) % a);
			}
		}
		else
		{
			cout << "sorry" << endl;
		}
	}
	return 0;
}

这里呢主要是注意输出有一个条件就是x要是一个非负整数；

对于这种情况，首先我们要进行一次判断：若x>0;则直接输出；若x<0,则需要进行一些变化；

因为当这种情况下成立时；a(x+bn)+b(y-an)=1也是成立的；

于是我们进行变换；x=(x%b+b)%b;y=(y%a-a)%a;就行了；