UVa 10338 - Mischievous Children

#include <bits/stdc++.h>
#define LL  long long
#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(),(x).end()
#define REP(i,n) for(int i=0;i<n;i++)
#define REV(i,n) for(int i=n-1;i>=0;i--)
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define pri(a) cout<<a<<endl
#define priii(a,b,c) cout<<a<<" "<<b<< " " <<c << endl
#define hi printf("Hello World\n");
using namespace std;

const int INF = 1<<29;
const int MX  = 1e5+10;

/// how many ways can the chars of a string be rearranged including its own arrangement?? 
/// total str size's factorial / (product of all repetitive chars' individual factorial)

LL fact[25];

void f()
{
    fact[0]=1;
    FOR(i,1,22)
    {
        fact[i]=fact[i-1]*i;
    }
}

int main()
{
    f();

    int T,cs=0;
    string s;
    cin>>T;
    while(T--)
    {
        cin>>s;

        int a[26]={0};  ///*

        REP(i,SZ(s))
        {
            a[ s[i]-'A']++;
        }

        LL ways = fact[SZ(s)];

        REP(i,26) ways /= fact[a[i]];

        printf("Data set %d: ", ++cs);
        pri(ways);
    }
        return 0;
}