Orz
by ListenSnow @ 2022-09-08 20:53:38
Orz
by Democlight @ 2022-09-08 20:59:13
```cpp
# include <bits/stdc++.h>
# define int long long
# define wheneveright signed main
using namespace std;
const int maxn = 5005;
const int mod = 1000000007;
int KSM (int x, int y = mod - 2) {
int ret = 1;
while (y) {
if (y & 1) ret = ret * x % mod;
x = x * x % mod; y >>= 1;
}
return ret % mod;
}
int n, res, odd;
int fac[maxn], inv[maxn];
char s[maxn];
int cnt[27];
wheneveright () {
scanf ("%lld%s", & n, s + 1); fac[0] = inv[0] = 1;
for (int i = 1; i <= n; i++) inv[i] = KSM (fac[i] = fac[i - 1] * i % mod);
for (char i : s) cnt[i - 'a']++;
for (int i = 0; i < 26; i++) odd += cnt[i] & 1;
if (odd > 1) { printf ("%lld\n", fac[n] % mod); return 0; }
odd = 1;
for (int i = 0; i < 26; i++) if (cnt[i] & 1) odd = cnt[i]; res = fac[n / 2] * odd % mod;
for (int i = 0; i < 26; i++) res = res * fac[cnt[i]] % mod * inv[cnt[i] / 2] % mod;
res = fac[n] - res;
printf ("%lld\n", (res % mod + mod) % mod);
return 0;
}
```
by Micnation_AFO @ 2022-09-08 21:03:13
@[wheneveright](/user/189351) 不过还是 WA 70pts，剩下的我不会了/kk
by Micnation_AFO @ 2022-09-08 21:05:57
@[Leap_hash_jperm](/user/574944) 谢谢，刚刚也发现这个问题了， Linux 环境不同的问题
by wheneveright @ 2022-09-08 21:11:01