Cod sursă (job #800604)

#include <fstream>
#include <cstring>

using namespace std;

ifstream cin("cristela.in");
ofstream cout("cristela.out");

long long A[(1<<21)];

int main()
{
    int n;
    char s[20];
    int sigma=0;
    cin>>n;
    for(int i=0;i<n;i++)
    {
        cin>>s;
        int x=strlen(s);
        int nr=0;
        for(int j=0;j<x;j++)
        {
            if(s[j]-'a'>sigma)
                sigma=s[j]-'a';
            nr=nr|(1<<s[j]-'a');
        }
        A[nr]++;
    }
    unsigned long long cnt=0;
    for(int i=0;i<(1<<sigma+1);i++)
    {
        if(A[i])
        {
            cnt+=A[i]*(A[i]-1)/2;
            for(int j=0;j<i;j++)
                if(A[j])
                {
                    if(i&j)
                    cnt+=A[i]*A[j];
                }
        }
        
    }
    cout<<cnt;
    

    return 0;
}