Lib/区別しない集合に分ける全列挙

code:cpp

ll n;

void p(vector<ll> v) {

for (ll a : v) cout << (char)('a' + a);

cout << endl;

return;

}

void saiki(vector<ll> v, ll k) {

if (v.size() == n) {

p(v);

return;

}

rep(i, k + 1) {

v.push_back(i);

ll next = (i == k) ? k + 1 : k;

saiki(v, next);

v.pop_back();

}

}

signed main() {

cin >> n;

vector<ll> v;

saiki(v, 0);

}

当然 O(N!)