Submission #1815487

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Source Code Expand

#include <cstdio>
#include <cstring>
#define MAXN 210
#define LL long long

const LL P=998244353;

LL getPow(LL x,LL y){
	LL res=1;
	while(y){
		if(y&1) res=res*x%P;
		x=x*x%P;
		y>>=1;
	}
	return res;
}

struct vec2{
	int x,y;
	vec2(int _x=0,int _y=0):x(_x),y(_y){}
	friend vec2 operator-(vec2 x,vec2 y){ return vec2(x.x-y.x,x.y-y.y); }
	friend int dot(vec2 x,vec2 y){ return x.x*y.x+x.y*y.y; }
	friend int cross(vec2 x,vec2 y){ return x.x*y.y-x.y*y.x; }
}p[MAXN];

int n;

int main(){
#ifdef DEBUG
	freopen("E.in","r",stdin);
#endif
	LL inv2=getPow(2,P-2);
	scanf("%d",&n);
	for(int i=1;i<=n;i++) scanf("%d%d",&p[i].x,&p[i].y);
	LL ans=getPow(2,n);
	LL res=0;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			if(i^j){
				vec2 d=p[j]-p[i];
				int cnt=2;
				for(int k=1;k<=n;k++)
					if(cross(p[k]-p[j],d)==0 && k!=i && k!=j){
						if(dot(p[k]-p[j],d)<0){
							cnt=0;
							break;
						}
						cnt++;
					}
				LL temp=getPow(2,cnt)-cnt-1;
				res=(res+temp)%P;
			}
	res=res*inv2%P;
	res=(res+n+1)%P;
	ans-=res;
	ans=(ans%P+P)%P;
	printf("%lld\n",ans);
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:33:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
                ^
./Main.cpp:34:53: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1;i<=n;i++) scanf("%d%d",&p[i].x,&p[i].y);
                                                     ^

Judge Result