今天的模拟也太毒瘤了……
T1 permutation
期望得分：20
实际得分：20
我刚开始是这么想的：T1嘛，应该不会太难，想想正解吧。本来想求出所有不合法的情况，然后用n!减一下。于是用dp，但发现这玩意是有后效性的，硬推了将近一个点儿，最终还是放弃了。只能20分全排列暴力了……
正解完全没看懂，居然成了什么二分图的补图，然后还用什么卷积……弃疗了
20分的
1 #include<cstdio> 2 #include<iostream> 3 #include<cmath> 4 #include<algorithm> 5 #include<cstring> 6 #include<cstdlib> 7 #include<cctype> 8 #include<vector> 9 #include<stack> 10 #include<queue> 11 using namespace std; 12 #define enter puts("") 13 #define space putchar(' ') 14 #define Mem(a, x) memset(a, x, sizeof(a)) 15 #define rg register 16 typedef long long ll; 17 typedef double db; 18 const int INF = 0x3f3f3f3f; 19 const db eps = 1e-8; 20 const int maxn = 12; 21 const ll mod = 998244353; 22 inline ll read() 23 { 24 ll ans = 0; 25 char ch = getchar(), last = ' '; 26 while(!isdigit(ch)) {last = ch; ch = getchar();} 27 while(isdigit(ch)) {ans = ans * 10 + ch - '0'; ch = getchar();} 28 if(last == '-') ans = -ans; 29 return ans; 30 } 31 inline void write(ll x) 32 { 33 if(x < 0) x = -x, putchar('-'); 34 if(x >= 10) write(x / 10); 35 putchar(x % 10 + '0'); 36 } 37 38 int n, k, a[maxn]; 39 ll ans = 0; 40 41 ll fac[maxn * 10000]; 42 void work0() 43 { 44 fac[1] = 1; 45 for(int i = 2; i <= n; ++i) fac[i] = fac[i - 1] * i % mod; 46 write((fac[n] - fac[n - 1]) % mod); enter; 47 } 48 49 int main() 50 { 51 freopen("permutation.in", "r", stdin); 52 freopen("permutation.out", "w", stdout); 53 n = read(); k = read(); 54 if(n > 10) {work0(); return 0;} 55 for(rg int i = 1; i <= n; ++i) a[i] = i; 56 do 57 { 58 bool flg = 1; 59 for(rg int i = 1; i <= n; ++i) if(abs(a[i] - i) == k) {flg = 0; break;} 60 if(flg) ans++; 61 }while(next_permutation(a + 1, a + n + 1)); 62 write(ans % mod); enter; 63 return 0; 64 }