[类欧几里得算法 数论] BZOJ 2987 Earthquake

第一道类欧题 其实是裸题啦

手推

#include
#include
#include
using namespace std;
typedef long long ll;

inline char nc(){
	static char buf[100000],*p1=buf,*p2=buf;
	if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }
	return *p1++;
}

inline void read(ll &x)
{
	char c=nc(),b=1;
	for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;
	for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;
}

inline ll Solve(ll n,ll a,ll c,ll b){
	if (!a)
		return (c/b)*n;
	if (c<0){
		ll t=(-c+b-1)/b;
		return Solve(n,a,c+t*b,b)-t*n;
	}
	if (b<=c)
		return Solve(n,a,c%b,b)+n*(c/b);
	if (a>=b)
		return n*(n+1)/2*(a/b)+Solve(n,a%b,c,b);
	ll kmax=(c+a*n)/b;
	ll ret=(n+1)*kmax;
	ret-=Solve(kmax,b,a-1-c,a);
	return ret;
}

ll ans;

int main()
{
	ll a,b,c;
	freopen("t.in","r",stdin);
	freopen("t.out","w",stdout);
	read(a); read(b); read(c);
	ans=(c/b)+(c/a)+1+Solve(c/a,a,c%a-a,b);
	printf("%lld\n",ans);
	return 0;
}