IITKWPCH-Find Number Of Pair of Friends

Find Number Of Pair of Friends

given below code is for iitkwpch spoj & find number of pair of friends spoj
in the given problem two number are friend if two number have atlest two digit in common.
now i have taken an array of size 10 and initalize it with all zero now i am scaning number and if any digit is encountered then then i will make array element 1 at that position
eg:
for number  11 there is two 1 so make 1 at position 1;

0

0

0

0

0

0

0

0

1

0

now its decimal will be 2 so i will increament the array a at position two
& for 35

0

0

0

0

1

0

1

0

0

0

its decimal is 40 so i will increament the array a[] at position 40;

now i am pairing for digit  occurance of number in two nested for loop I have started with position 0

of i & j; condition is given i<j so and not to check number with itself and condition (i & j) is for that if number have atleast one common digit or not

eg

for position 35 and 11

condition (35 & 11) will be false because number are having no common digit
in single for loop i am checking occurence of sane number if given condition is
1
10
1 1 1 1 1 1 1 1 1 1
then possible pairs are n(n-1)/2;
since the two nested loop is reversely repeated so all pairs will occure wice so in last i am dividing it by 2;

#include <stdio.h>
#include <iostream>
#include <cstdlib>
#define LL long long
using namespace std;
int main()
{
 int t;
 scanf("%d",&t);
 while(t--)
 {
  int n,i,j,num=0;
  scanf("%d",&n);
  LL temp,total=0;
  LL *a=(LL *)calloc(1200,sizeof(LL));
  int dig[10]={0};
  while(n--)
  {
   scanf("%lld",&temp);
   while(temp)
   {
    num=num | (1<<temp%10);
    temp/=10;
   }
   a[num]++;
   num=0;
  }
  for(i=1;i<1024;i++)
  {
   for(j=1;j<1024;j++)
   {
    if(i!=j && (i&j)){
     total+=a[i]*a[j];
    }
   }
  }
  for(i=1;i<1024;i++)
   total+=(a[i]*(a[i]-1));
  printf("%lld\n",total/2);
 }
 return 0;
}