Building Strings

#include <bits/stdc++.h>
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define MOD (int) 1e9 + 7
#define all(x) begin(x), end(x)
typedef long long ll;
using namespace std;
template <typename T> // cin >> vector<T>
istream &operator>>(istream &istream, vector<T> &v) {
    for (auto &it : v)
        cin >> it;
    return istream;
}
template <typename T> // cout << vector<T>
ostream &operator<<(ostream &ostream, const vector<T> &c) {
    for (auto &it : c)
        cout << it << " ";
    return ostream;
}

int k;
vector<vector<char>> subsets;

void rec(vector<char>& v, int i) {
    if(i == 11) return;
    if(v.size() == k) {
        subsets.push_back(v);
    }
    else {
        rec(v, i + 1);
        v.push_back('a' + i);
        rec(v, i + 1);
        v.pop_back();
    }    
}

bool check(vector<char> v, string s) {
    for(int i = 0; i < s.length(); i++) {
        bool flag = false;
        for(int j = 0; j < v.size(); j++) {
            if(s[i] == v[j]) {
                flag = true;
                break;
            }
        }
        if(!flag) return false;
    }
    return true;
}

void solve(void) 
{
    int n; cin >> n >> k;
    vector<char> v;
    rec(v, 0);
    vector<string> s(n); cin >> s;
    int ans = 0;
    for(auto x : subsets) {
        int tmp = 0;
        for(int i = 0; i < n; i++) {
            if(check(x, s[i])) {
                tmp++;
            }
        }
        ans = max(ans, tmp);
    }
    cout << ans << '\n';
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    solve();
    return 0;
}