C++ check if given points make square - c++

Question

I have 4 points given, I have to check if its square AND its collateral to the x and y axis.
Here is my code:
#include <cstdlib>
#include <iostream>
#include <cmath>
using namespace std;
int wasIn(int x, int n[2])
{
for (int i=0; i<2; i++)
if (x==n[i]) return i;
return -1;
}
int main(int argc, char *argv[])
{
int x[4];
int y[4];
for (int i=0; i<4; i++)
cin>>x[i]>>y[i];
int was[2];
was[0]=-1001;
was[1]=-1001;
int countwas[2];
countwas[0]=0;
countwas[1]=0;
short old=0;
bool ok=true;
int tmp;
for (int i=0; i<4; i++)
{
if ((tmp=wasIn(x[i],was))==-1) {was[old]=x[i]; old++;} else countwas[tmp]++;
if ((tmp=wasIn(y[i],was))==-1) {was[old]=y[i]; old++;} else countwas[tmp]++;
if (old>2) { ok=false; break; }
}
if (ok && countwas[1]!=3 || countwas[0]!=3) ok=false;
//cout<<"C1: "<<countwas[0]<<endl; //debug
//cout<<"C2: "<<countwas[1]<<endl;
if (ok) cout<<"YES"; else cout<<"NO";
//system("PAUSE");
return EXIT_SUCCESS;
}
How it works:
just checks if there are 2 different numbers only, and there are exacly 4 (decrased by 1st point, so in program its 3) same occurences.
Thanx for any replies.
It sometimes crashes and gives wrong output... Maybe index out of bounds?

Answer 1

I won't fix your code, but the algorithm is really simple:
Check if the topleft point is on the same horizontal line as the topright point, and on the same vertical line as the bottomleft point.
Check if the bottomright point is on the same horizontal line as the bottomleft point and on the same vertical line as the topright point.
If both are true you are dealing with a collateral rectangle.
Now, if you need to know if it's a square you need to add one more check, whether the horizontal side is just as large as the vertical side.

Answer 2

Finally did it. I used another idea. I took the two different values x or y, generated the correct square based on that 2 numbers and compared to given. Code if someone needs:
#include <cstdlib>
#include <iostream>
#include <cmath>
using namespace std;
int isIn(int x, int n[2])
{
for (int i=0; i<2; i++)
if (x==n[i]) return i;
return -1;
}
int cmpPoint(int x, int y, int xt[4], int yt[4])
{
for (int i=0; i<4; i++)
if (x==xt[i] && y==yt[i]) return i;
return -1;
}
int main(int argc, char *argv[])
{
int x[4];
int y[4];
for (int i=0; i<4; i++)
cin>>x[i]>>y[i];
int dif[2]={-1001,-1001};
short act=-1;
short tmp;
for (int i=0; i<4; i++)
{
if ((tmp=isIn(x[i],dif))==-1) {act++; dif[act]=x[i];}
if (act>1) break;
if ((tmp=isIn(y[i],dif))==-1) {act++; dif[act]=y[i];}
if (act>1) break;
}
if (act!=1)
{
cout<<"NO";
return 0;
}
int x2[4];
int y2[4];
bool was[4]={0,0,0,0};
x2[0]=dif[0];
y2[0]=dif[0];
x2[1]=dif[1];
y2[1]=dif[0];
x2[2]=dif[0];
y2[2]=dif[1];
x2[3]=dif[1];
y2[3]=dif[1];
bool ok=true;
for (int i=0; i<4; i++)
{
tmp=cmpPoint(x[i],y[i],x2,y2);
if (was[tmp]) {ok=false; break;}
else was[tmp]=true;
}
if (ok) cout<<"YES"; else cout<<"NO";
//system("PAUSE");
return EXIT_SUCCESS;
}