Submission #3407

#	Time	Username	Problem	Language	Result	Execution time	Memory
3407		cki86201	Divide into triangle (kriii1_D)	C++98	0 / 1	0 ms	1324 KiB

D

#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<vector>
#include<math.h>
#include<stdlib.h>
using namespace std;

struct point{
	point(){}
	point(int x,int y):x(x),y(y){}
	int x,y;
	bool operator<(const point &l)const{return x!=l.x?x<l.x:y<l.y;}
}p[920];

int N;
bool check[920];
int o[920];

bool comp(const int &a,const int &b)
{
	return p[a]<p[b];
}

void solve(int x)
{
	int i,p1=0,p2=0;
	check[x]=1;
	double a1,a2;
	for(i=1;i<=3*N;i++){
		if(check[i])continue;
		if(p1==0 && p2==0){a1=atan2(p[i].y-p[x].y, p[i].x-p[x].x);p1=i;continue;}
		if(p2==0){a2=atan2(p[i].y-p[x].y, p[i].x-p[x].x);p2=i;continue;}
		double f = atan2(p[i].y-p[x].y, p[i].x-p[x].x);
		if(f<a1){a2=a1;p2=p1;a1=f;p1=i;continue;}
		if(f<a2){a2=f;p2=i;continue;}
	}
	check[p1]=check[p2]=1;
	printf("%d %d %d\n",x,p1,p2);
}

int main()
{
	int i;
	scanf("%d",&N);
	for(i=1;i<=3*N;i++){
		scanf("%d%d",&p[i].x,&p[i].y);
	}
	for(i=1;i<=3*N;i++)o[i]=i;
	sort(o+1,o+1+3*N,comp);
	for(i=1;i<=3*N;i++){
		if(check[o[i]])continue;
		solve(o[i]);
	}
	return 0;
}

• Subtask 1: 0 / 1