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-y2B=x2-x1C=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;}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + a;result = prime * result + b;result = prime * result + c;return result;}@Overridepublic 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{@Overridepublic 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);}}