Codeforces Beta Round #18 (Div. 2 Only)——A

A. Triangle

time limit per test
2 seconds

memory limit per test
64 megabytes

input
standard input

output
standard output

At a geometry lesson Bob learnt that a triangle is called right-angled if it is nondegenerate and one of its angles is right. Bob decided to draw such a triangle immediately: on a sheet of paper he drew three points with integer coordinates, and joined them
with segments of straight lines, then he showed the triangle to Peter. Peter said that Bob's triangle is not right-angled, but is almost right-angled: the triangle itself is not right-angled,
but it is possible to move one of the points exactly by distance 1 so, that all the coordinates remain integer, and the triangle become right-angled. Bob asks you to help him and find out if Peter tricks him. By the given coordinates of the triangle you should
find out if it is right-angled, almost right-angled, or neither of these.

Input

The first input line contains 6 space-separated integers x1, y1, x2, y2, x3, y3 —
coordinates of the triangle's vertices. All the coordinates are integer and don't exceed 100 in absolute value. It's guaranteed that the triangle is nondegenerate, i.e. its total area is not zero.

Output

If the given triangle is right-angled, output RIGHT, if it is almost right-angled, output ALMOST,
and if it is neither of these, outputNEITHER.

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <cmath>
#define maxn 5
using namespace std;

struct node
{
int x,y;
} a[maxn];
int dx[4]= {-1,0,1,0},dy[4]= {0,-1,0,1}; //四个方向坐标
int dis(int x1,int y1,int x2,int y2)
{
return  (x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);//You should use squared distances instead of taking roots to overcome problems related to precision errors
}
bool isright(int x1,int y1,int x2,int y2,int x3,int y3)
{
int s1=dis(x1,y1,x2,y2);
int s2=dis(x2,y2,x3,y3);
int s3=dis(x1,y1,x3,y3);
if(s1==0||s2==0||s3==0) return 0;
if(s1==s2+s3||s2==s1+s3||s3==s1+s2) return 1;
else return 0;
}
int main()
{
bool flag=false;
for(int i=1; i<=3; i++) scanf("%d%d",&a[i].x,&a[i].y);
if(isright(a[1].x,a[1].y,a[2].x,a[2].y,a[3].x,a[3].y))
{
printf("RIGHT\n");
return 0;
}
else
{

for(int i=0; i<4; i++)
{
int x=a[1].x+dx[i],y=a[1].y+dy[i];
if(isright(x,y,a[2].x,a[2].y,a[3].x,a[3].y)) flag=true;
}
for(int i=0; i<4; i++)
{
int x=a[2].x+dx[i],y=a[2].y+dy[i];
if(isright(x,y,a[1].x,a[1].y,a[3].x,a[3].y)) flag=true;
}
for(int i=0; i<4; i++)
{
int x=a[3].x+dx[i],y=a[3].y+dy[i];
if(isright(x,y,a[2].x,a[2].y,a[1].x,a[1].y)) flag=true;
}
}
if(flag) printf("ALMOST\n");
else printf("NEITHER\n");
return 0;
}