Submission #474405

#	Time	Username	Problem	Language	Result	Execution time	Memory
474405		hhhhaura	Cat (info1cup19_cat)	C++14	0 / 100	32 ms	1392 KiB

cat

#define wiwihorz
#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma loop-opt(on)

#define rep(i, a, b) for(int i = a; i <= b; i ++)
#define rrep(i, a, b) for(int i = b; i >= a; i--)
#define all(x) x.begin(), x.end()
#define ceil(a, b) ((a + b - 1) / (b))

using namespace std;

#define int long long int
#define lld long double
#define pii pair<int, int>
#define random mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count())

#ifdef wiwihorz
#define print(a...) cerr << "Line: " << __LINE__, kout("[" + string(#a) + "] = ", a)
void vprint(auto L, auto R) { while(L < R)cerr << *L << " \n"[next(L) == R], ++L; }
void kout() { cerr << endl; }
template<class T1, class ... T2> void kout(T1 a, T2 ... e) { cerr << a << " ", kout(e...);}
#else
#define print(...) 0
#define vprint(...) 0
#endif
namespace solver {
	int n;
	vector<int> a, vis, b, sim;
	vector<pii> ans;
	void init_(int _n) {
		n = _n;
		a.assign(n + 1, 0);
		vis.assign(n + 1, 0);
		sim.assign(n + 1, 0);
	}
	void solve() {
		sim = a;
		rep(i, 1, n / 2) {
			if(a[i + n / 2] - n / 2 != a[i]) {
				cout << "-1\n";
				return;
			}
		}
		int cnt = 0;
		rep(i, 1, n / 2) if(a[i] != i && !vis[i]) {
			int cur = a[i];
			b.clear();
			b.push_back(i);
			vis[i] = 1;
			while(cur != i) {
				b.push_back(cur);
				vis[cur] = 1;
				cur = a[cur];
			}
			rep(j, 0, signed(b.size()) - 2) {
				ans.push_back({b[j], b[j + 1]});
			}
		}
		cout << ans.size() << "\n";
		for(auto i : ans) {
			cout << i.first << " " << i.second << "\n";
			swap(sim[i.first], sim[i.second]);
			swap(sim[n - i.first + 1], sim[n - i.second + 1]);
		}
		return;		
	}
};
using namespace solver;
signed main() {
	ios::sync_with_stdio(false), cin.tie(0);
	int t; cin >> t;
	while(t--) {
		int n; cin >> n;
		init_(n);
		rep(i, 1, n) cin >> a[i];
		solve();
	}
	return 0;
}

Compilation message (stderr)

cat.cpp:4: warning: ignoring '#pragma loop ' [-Wunknown-pragmas]
    4 | #pragma loop-opt(on)
      | 
cat.cpp:20:13: warning: use of 'auto' in parameter declaration only available with '-fconcepts-ts'
   20 | void vprint(auto L, auto R) { while(L < R)cerr << *L << " \n"[next(L) == R], ++L; }
      |             ^~~~
cat.cpp:20:21: warning: use of 'auto' in parameter declaration only available with '-fconcepts-ts'
   20 | void vprint(auto L, auto R) { while(L < R)cerr << *L << " \n"[next(L) == R], ++L; }
      |                     ^~~~
cat.cpp: In function 'void solver::solve()':
cat.cpp:45:7: warning: unused variable 'cnt' [-Wunused-variable]
   45 |   int cnt = 0;
      |       ^~~

• Subtask 1: 0 / 15
• Subtask 2: 0 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 15
• Subtask 5: 0 / 35