Submission #3708280

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Source Code Expand

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<algorithm>
#include<math.h>
using namespace std;

const double eps=1e-6;
int N,top;
struct node
{
	double x,y;
};
node n[100005],dot[100005];

double dis(node a,node b)
{
	return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}

double S(node a,node b,node c)
{
	node X,Y;
	X.x=b.x-a.x;
	X.y=b.y-a.y;
	Y.x=c.x-a.x;
	Y.y=c.y-a.y;
	return fabs(X.x*Y.y-X.y*Y.x);
}

bool my_comp(node a,node b)
{
	double X=(a.x-n[1].x)*(b.y-n[1].y);
	double Y=(a.y-n[1].y)*(b.x-n[1].x);
	double Z=X-Y;
	if(fabs(Z)<=eps)
		if(dis(n[1],a)<dis(n[1],b)) return true;
		else return false;
	else
		return Z>0?true:false;
}

void init()
{
	int i;
	scanf("%d",&N);
	for(i=1;i<=N;++i) scanf("%lf%lf",&n[i].x,&n[i].y);
}

bool ok(int i)
{
	double X=(dot[top].x-dot[top-1].x)*(n[i].y-dot[top-1].y);
	double Y=(dot[top].y-dot[top-1].y)*(n[i].x-dot[top-1].x);
	if(X-Y<eps) return true;
	else return false;
}

void graham()
{
	int i,j;
	
	for(i=2;i<=N;++i)
		if(n[i].y-n[1].y<eps||fabs(n[i].y-n[1].y)<eps&&n[i].x-n[1].x<eps)
		{
			swap(n[i].x,n[1].x);
			swap(n[i].y,n[1].y);
		}
	sort(n+2,n+N+1,my_comp);

	dot[0]=n[1],dot[1]=n[2];
	top=1;
	for(i=3;i<=N;++i)
	{
		while(top>0&&ok(i)) --top;
		dot[++top]=n[i];
	}
}

double rotate()
{
	double ret=0.0;
	int i,j;
	
	j=2;++top;
	for(i=0;i<top;++i)
	{
		while(S(dot[i],dot[(i+1)%top],dot[j])<S(dot[i],dot[(i+1)%top],dot[(j+1)%top]))
			j=(j+1)%top;
		ret=max(ret,dis(dot[j],dot[i]));
		ret=max(ret,dis(dot[j],dot[(i+1)%top]));
	}
	
	return ret;
}
int main()
{
//	freopen("dotfar.in","r",stdin);
//	freopen("dotfar.out","w",stdout);
	
	init();
	graham();
	printf("%.6lf\n",rotate());
	
	fclose(stdin);
	fclose(stdout);
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘void init()’:
./Main.cpp:48:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&N);
                ^
./Main.cpp:49:51: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  for(i=1;i<=N;++i) scanf("%lf%lf",&n[i].x,&n[i].y);
                                                   ^

Judge Result