P2421 [NOI2002]荒岛野人 扩展欧几里得 枚举

Code:

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
typedef long long ll;
int N;
struct Node{
	ll C,P,L;
}nodes[20];
ll abss(ll a){return a<0?-a:a;}
ll exgcd(ll a,ll b,ll &x,ll &y){
	if(b==0){x=1,y=0;return a;}
	ll ans=exgcd(b,a%b,x,y);
	ll tmp=x;
	x=y,y=tmp-a/b*y;
	return ans;
}
int check(int M){
	for(int i=1;i<N;++i)
		for(int j=i+1;j<=N;++j)
		{
			ll a=nodes[i].P-nodes[j].P,b=M,c=nodes[j].C-nodes[i].C;
			ll x,y,mod,ans;
			ans=exgcd(a,b,x,y);
			if(c%ans!=0)continue;
			x*=(c/ans);
			mod=abss(b/ans);
			x=((x%mod)+mod)%mod;
			if(x<=nodes[i].L&&x<=nodes[j].L)return 0;
		}
	return 1;
}
int main(){
	//freopen("in.txt","r",stdin);
	ll u=0;
	scanf("%d",&N);
	for(int i=1;i<=N;++i){
		scanf("%lld%lld%lld",&nodes[i].C,&nodes[i].P,&nodes[i].L);
		u=max(u,nodes[i].C);
	}
	int ans=u;
	for(;;++ans)if(check(ans))break;
	printf("%d",ans);
	return 0;
}