代码

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <ctime>
#define re register

const int mod = 998244353;
using namespace std;

int num = 0,n;
int s[166],a[166],c[166];

inline bool work() {
	int num = 0,k = 0;
	for( re int i = 1;i <= n;++ i) 
		num += abs(i - s[i]);
	for(re int i = 1;i <= n;++ i) {
		for( re int j = 1;j < n;++ j) {
			if(s[j] > s[j + 1]) {
				swap(s[j],s[j + 1]);
				k ++;
			}
		}
	}
	return k == (num / 2) ? true : false;
}

int main() {
//	freopen("gg.in","r",stdin);
	int T;
	scanf("%d",&T);
	while(T --) {
		int ans = 0;
		scanf("%d",&n);
		for(re int i = 1;i <= n;++ i) { 
			scanf("%d",&a[i]);
			s[i] = a[i];
		}
		while(next_permutation(s + 1,s + 1 + n)) {
			for(re int i = 1;i <= n;++ i) 
				c[i] = s[i];
			if(work()) ans ++;
			for(re int i = 1;i <= n;++ i) 
				s[i] = c[i];
		}
		printf("%d\n",ans);
	}
	return 0;
}

评测结果