#include <bits/stdc++.h> using namespace std; const int N = 2000 + 10, M = 1'000'000'007; int n, k; string s[N]; inline void add(auto& x, const auto& y) { x += y; if (x >= M) x -= M; } inline int powder(int a, int b) { int ret = 1; for (; b; b /= 2, a = 1ll * a * a % M) { if (b & 1) ret = 1ll * ret * a % M; } return ret; } int fac[N], ifac[N]; inline int C(int n, int k) { return 1ll * fac[n] * ifac[n - k] % M * ifac[k] % M; } int f[N][N]; int32_t main() { cin.tie(0)->sync_with_stdio(0); if (fopen("input.txt", "r")) { freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout); } if (fopen("anagramistica.inp", "r")) { freopen("anagramistica.inp", "r", stdin); freopen("anagramistica.out", "w", stdout); } cin >> n >> k; for (int i = 1; i <= n; ++i) cin >> s[i]; for (int i = 1; i <= n; ++i) { sort(s[i].begin(), s[i].end()); } sort(s + 1, s + n + 1); vector<int> vt; { // cal vt string last; for (int i = 1; i <= n; ++i) { if (s[i] != last) last = s[i], vt.push_back(0); vt.back() += 1; } } { // init fact fac[0] = 1; for (int i = 1; i < N; ++i) fac[i] = 1ll * fac[i - 1] * i % M; ifac[N - 1] = powder(fac[N - 1], M - 2); for (int i = N - 1; i >= 1; --i) ifac[i - 1] = 1ll * ifac[i] * i % M; } vt.insert(vt.begin(), 0); f[0][0] = 1; for (int i = 1; i < (int)vt.size(); ++i) { for (int j = 0; j <= k; ++j) { auto& ret = f[i][j]; for (int choose = 0; choose <= vt[i]; ++choose) { int pii = choose * (choose - 1) / 2; if (pii > j) break; add(ret, 1ll * f[i - 1][j - pii] * C(vt[i], choose) % M); } } } cout << f[vt.size() - 1][k] << "\n"; }

anagramistica.cpp: In function 'int32_t main()':
anagramistica.cpp:31:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |         freopen("input.txt", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
anagramistica.cpp:32:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   32 |         freopen("output.txt", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
anagramistica.cpp:35:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |         freopen("anagramistica.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
anagramistica.cpp:36:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |         freopen("anagramistica.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~