代码

#include<cstdio>
#include<map>
#include<cstring>
#include<queue>
#include<algorithm>
#define rg register 
using namespace std;
const int MAXN = 11, INF = 1e9 + 10, mod = 998244353;
inline int read() {
	char c = getchar(); int x = 0, f = 1;
	while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
	while(c >= '0' && c <= '9')x = x * 10 + c - '0', c = getchar();
	return x * f;
}
int QwQ, N, a[MAXN], ed[MAXN];
int pd(int *a, int *b) {
	for(rg int i = 1; i <= N; i++)
		if(a[i] != b[i]) return 0;
	return 1;
}
bool calc() {
	rg int times = 0, num = 0;
	for(rg int i = 1; i <= N; i++) num += abs(i - a[i]);
	for(rg int i = 1; i <= N; i++) 
		for(rg int j = i - 1; j >= 1; j--)
			if(a[i] < a[j]) times++;
	return (times * 2) == num;
}
int main() {
	QwQ = read();
	while(QwQ--) {
		N = read();
		for(rg int i = 1; i <= N; i++) a[i] = read(), ed[i] = N - i + 1;
		int ans = 0;
		next_permutation(a + 1, a + N + 1);
		while(!pd(a, ed)) 
			ans += calc(), next_permutation(a + 1, a + N + 1);
		printf("%d\n", ans);
	}
	return 0;
}
/*
5
10
1 2 3 4 5 6 7 8 9 10
10
1 2 3 4 5 6 7 8 9 10
10
1 2 3 4 5 6 7 8 9 10
10
1 2 3 4 5 6 7 8 9 10
10
1 2 3 4 5 6 7 8 9 10
*/

评测结果