K - Counting Good Teams

#include <bits/stdc++.h>

#define pb push_back

using namespace std;

typedef long long ll;
typedef vector<int> vi;

ll v1[1<<22];
ll v2[1<<22];
ll eq[1<<22];
vi v;

int main() {
    ll n, m;
    cin >> n >> m;
    for(int i = 0; i < n; i++) {
        int aux;
        cin >> aux;
        v.pb(aux);
    }
    int h1 = m/2;
    int h2 = m - h1;
    for(int i = 0; i < n; i++) {
        int h1mask = v[i] >> h2;
        h1mask = h1mask << h2;
        int h2mask = ((1 << h2) - 1) & v[i];
        int h2maskcp = ((1 << h2) - 1) & (~h2mask);

        for(int j = h1mask; j; j = (j - 1)&h1mask){
            v1[j + h2mask]++;
        }
        v1[h2mask]++;
        for(int j = h2maskcp; j; j = (j - 1)&h2maskcp){
            v2[j + h2mask + h1mask]++;
        }
        v2[h2mask + h1mask]++;
        eq[v[i]]++;
    }
    ll ans = 0;
    for(int i = 0; i < (1 << m); i++) {
        ans += v1[i]*v2[i];
        ans -= (eq[i]*(eq[i]-1))/2;
    }
    ans -= n;
    cout << (n * (n-1))/2 - ans << endl;
    return 0;
}