Program 360: Print all possible squares from given N Co-ordinates

Program 360: Print all possible squares from given N Co-ordinates
 

#include<stdio.h>
struct Vertex
{
 int x, y;
};
void CombiPossible(int arr[], int data[], int start, int end,int index, int r,int allCombinations[]);
int CheckSquare(Vertex p1, Vertex p2, Vertex p3, Vertex p4);
int DistVetrices(Vertex p, Vertex q);
int GetNcR(int n,int r);
int factorial(int num);
int main()
{
 int chkSquare,i,n,j,k,temp,r=4,l,count=0;
 char c;
 printf("Enter number of vertices\n");
 scanf("%d",&n);
 Vertex p[n];
 int arr[n];
 for(i=0;i<n;i++)
 {
  printf("Enter Vertices of %d in (x y) form\n",i);
  scanf("%d%c%d",&p[i].x,&c,&p[i].y);
  arr[i]=i;
 }
int data[r];
int ncr=GetNcR(n,r);
int allCombinations[ncr*4];
CombiPossible(arr,data, 0,n-1,0,r,allCombinations);
for(i=0;i<ncr*4;i+=4)
{
 //printf("%d--->%d,%d,%d,%d\n",i,allCombinations[i],allCombinations[i+1],allCombinations[i+2],allCombinations[i+3]);
 int num[4]={allCombinations[i],allCombinations[i+1],allCombinations[i+2],allCombinations[i+3]};
 chkSquare=CheckSquare(p[num[0]], p[num[1]], p[num[2]], p[num[3]]);
 if(chkSquare==1)
 {
  for(l=0;l<=r-1;l++)
    printf("(%d,%d), ",p[num[l]].x,p[num[l]].y);
    count++;
    printf("\n");
 }
}
printf("Total Squares Possibility=%d\n",count);
return 0;
}
int CheckSquare(Vertex p1, Vertex p2, Vertex p3, Vertex p4)
{
 int d2 = DistVetrices(p1, p2);
 int d3 = DistVetrices(p1, p3);
 int d4 = DistVetrices(p1, p4);
 if (d2 == d3 && 2*d2 == d4)
 {
  int flag=0;
  int d = DistVetrices(p2, p4);
  if(d == DistVetrices(p3, p4) && d == d2){
       flag=1; 
  }
  return (flag);
 }
 if (d3 == d4 && 2*d3 == d2)
 {
  int flag=0;
  int d = DistVetrices(p2, p3);
  if(d == DistVetrices(p2, p4) && d == d3)
      flag=1;
  return (flag);
 }
 if (d2 == d4 && 2*d2 == d3)
 {
  int flag=0;
  int d = DistVetrices(p2, p3);
  if(d == DistVetrices(p3, p4) && d == d2)
     flag=1;
  return (flag);
 }

 return (0);
}
int DistVetrices(Vertex p, Vertex q)
{
 return (p.x - q.x)*(p.x - q.x) +
  (p.y - q.y)*(p.y - q.y);
}

void CombiPossible(int arr[], int data[], int start, int end,int index, int r,int allCombinations[])
{
static int x=0;
    if (index == r)
    {
        for (int j=0; j<r; j++)
        {
         allCombinations[x++]=data[j];
        }
        return;
    }
    for (int i=start; i<=end && end-i+1 >= r-index; i++)
    {
        data[index] = arr[i];
        CombiPossible(arr, data, i+1, end, index+1, r,allCombinations);
    }
}

int GetNcR(int n,int r)
{
 return ((float)factorial(n)/(factorial(r)*factorial(n-r)));
}
 
int factorial(int num)
{
 int i,fact=1;
 for(i=1;i<=num;i++)
 {
  fact=fact*i;
 }
 
 return(fact);
}

Explanation:

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Output: