代码

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<cctype>
#include<vector>
#include<map>
#include<queue>
using namespace std;
typedef long long LL;

inline int read() {
    int x=0,f=1;char ch=getchar();for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-1;
    for (;isdigit(ch);ch=getchar())x=x*10+ch-'0';return x*f;
}

const int mod = 998244353;

int a[100010];
int b[100010];

void solve() {
	int n = read();
	LL Ans = 0;
	for (int i=1; i<=n; ++i) a[i] = read();
	while (next_permutation(a+1,a+n+1)) {
		for (int i=1; i<=n; ++i) b[i] = a[i];
		int cnt = 0,c = 0;
		for (int i=1; i<=n; ++i) cnt += abs(b[i] - i);
		cnt /= 2;
		for (int i=1; i<=n; ++i) 
			for (int j=1; j<n; ++j) {
				if (b[j] > b[j+1]) c++,swap(b[j],b[j+1]);
			}
		if (cnt == c) Ans++;
		if (Ans > mod) Ans = Ans % mod;
	} 
	printf("%lld\n",Ans % mod);
}

int main() {
	
	freopen("inverse.in","r",stdin);
	freopen("inverse.out","w",stdout);
	
	int Case = read();
	while (Case --) solve();	
	return 0;
}
/*
1
3
1 3 2


2
4
1 4 2 3
4
1 4 2 3
*/

评测结果