usaco-practice/cses/Create Strings.cpp

#include <algorithm>
#include <iostream>
using namespace std;

long find_fact(int num) {
  long num_perms = 1;
  for (int i = 0; i < num; i++) {
    num_perms *= num - i;
  }
  return num_perms;
}

int main() {
  string m;
  cin >> m;
  string n = m;
  sort(n.begin(), n.end());

  long num_perms = 1;
  int current_repetition = 1;
  for (int i = 0; i < n.length(); i++) {
    num_perms *= n.length() - i;
    if (i > 0) {
      if (n.at(i) == n.at(i - 1)) {
        current_repetition += 1;
      } else {
        if (current_repetition > 1) {
          num_perms /= find_fact(current_repetition);
        }
        current_repetition = 1;
      }
    }
  }
  if (current_repetition > 1) {
    num_perms /= find_fact(current_repetition);
  }

  cout << num_perms << endl;
  do {
    cout << n << endl;
  } while (next_permutation(n.begin(), n.end()));
}