第十二届蓝桥杯 直线 填空题 两种做法

答案：40257

由给定两点求直线的一般式Ax+By+C=0;
A=y1-y2
B=x2-x1
C=x1y2-x2y1

当保证AB互质时，三个参数唯一确定一条平面直线

解法一：用一般式表示直线，然后用set去重

import java.util.*;

public class Main
{
	static class line
	{
		int a,b,c;
		public line(int x,int y,int z)
		{
			a=x;b=y;c=z;
		}
		
		@Override
		public int hashCode() {
			final int prime = 31;
			int result = 1;
			result = prime * result + a;
			result = prime * result + b;
			result = prime * result + c;
			return result;
		}
		
		@Override
		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (obj == null)
				return false;
			if (getClass() != obj.getClass())
				return false;
			line other = (line) obj;
			if (a != other.a)
				return false;
			if (b != other.b)
				return false;
			if (c != other.c)
				return false;
			return true;
		}
	}
	static int gcd(int a,int b)
	{
		if(b==0)return a;
		return gcd(b,a%b);
	}
	
	static HashSet l=new HashSet<>();
	static int idx=0,ans=0;
	
	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);

		for(int x1=0;x1<20;x1++)
			for(int y1=0;y1<21;++y1)
				for(int x2=0;x2<20;++x2)
					for(int y2=0;y2<21;++y2)
					{
						if(x1==x2&&y1==y2)continue;
						int a,b,c,gcd;
						a=y1-y2;
						b=x2-x1;
						c=x1*y2-x2*y1;
						gcd=gcd(a,b);
						a/=gcd;
						b/=gcd;
						c/=gcd;
						l.add(new line(a,b,c));
					}
		System.out.println(l.size());
	}
}

import java.util.*;

public class Main
{
	static class line
	{
		double k,b;
		public line(double x,double y)
		{
			k=x;b=y;
		}
	}
	static class mcomp implements Comparator
	{

		@Override
		public int compare(line a, line bb) {
			if(Math.abs(a.k-bb.k)<1e-8)
			{
				if(a.b1e-6||Math.abs(l[i].b-l[i-1].b)>1e-6)
				res++;
		}
		res+=20;
		System.out.println(res);
		
	}
}