[Noi2002]Savage

[Noi2002]Savage

数学题。

题解回去写(有个坑点)

flag++

#include <cstdio>
int n,m,c[25],p[29],l[29];
int exgcd(int a,int b,int &x,int &y){
	if(!b){x=1,y=0;return a;}
	int ans=exgcd(b,a%b,x,y),t=x;
	x=y,y=t-a/b*y;
	return ans;
}
int max(int a,int b){return a>b?a:b;}
int min(int a,int b){return a<b?a:b;}
int gcd(int a,int b){return b?gcd(b,a%b):a;}
bool check(int ans){
	int x,y;
	for(int i=1;i<=n;i++){
		for(int j=i+1;j<=n;j++){
			int b=ans,a=p[j]-p[i],C=c[i]-c[j],g=gcd(a,b);x=0,y=0;
			if(C%g==0){
				a/=g,b/=g,C/=g;
				exgcd(a,b,x,y);
				b=b<0?-b:b;
				x=(x*C%b+b)%b;
				if(!x) x+=b;
				if(x<=min(l[i],l[j]))return 0;
			}
		}
	}
	return 1;
}
int main(){
	int mx=-1;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)scanf("%d%d%d",&c[i],&p[i],&l[i]),mx=max(mx,c[i]);
	for(int ans=mx;ans<=1e6;ans++)if(check(ans))return !printf("%d",ans);
}