Submission #315169

#	Time	Username	Problem	Language	Result	Execution time	Memory
315169		Kevin_Zhang_TW	Cat (info1cup19_cat)	C++17	51.25 / 100	585 ms	18036 KiB

cat

#include<bits/stdc++.h>
#define pb emplace_back
#define AI(i) begin(i), end(i)
using namespace std;
using ll = long long;
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void debug(auto L, auto R) { while (L < R) cerr << *L << " \n"[L+1==R], ++L; }
void kout(){ cerr << endl; }
template<class T1, class ...T2> void kout(T1 a, T2 ...e) { cerr << a << ' ', kout(e...); }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 3000010;
int per[MAX_N], n, pos[MAX_N];
void fail() {
	puts("-1"), exit(0);
}
void sw(int a, int b) {
	//DE(a, b, per[a], per[b]);
	swap(per[a], per[b]);
	swap(pos[per[a]], pos[per[b]]);
}
int rev(int i) {
	return n - i + 1;
}
vector< pair<int,int> > res;
bool part() {
	vector<int> L, R;
	int m = n / 2;
	for (int i = 1;i <= m;++i)
		if (per[i] > m)
			L.pb(i);
	for (int i = m+1;i <= n;++i)
		if (per[i] <= m)
			R.pb(i);

	assert(L.size() == R.size());

	reverse(AI(R));
	m = L.size();
	for (int i = 0;i < m;++i)
		if (L[i] != rev(R[i])) 
			return false;
	if (L.size()&1) {
		return false;
	}
	for (int i = 0;i < m;i += 2) {
		res.pb( L[i], R[i+1] );
		int a = L[i], b = R[i+1], c = rev(L[i]), d = rev(b);
		sw(a, b);
		sw(c, d);
	}
	return true;
}
void solve() {
	cin >> n;
	for (int i = 1;i <= n;++i)
		cin >> per[i], pos[per[i]] = i;
	res.clear();
	res.reserve(n);
	if (!part()) {
		cout << -1 << '\n';
		return;
	}
	int m = n / 2;

	DE(m);
	for (int i = 1;i <= m;++i) {
		while (i != per[i]) {
			int x = per[i];
			res.pb(i, pos[i]);
			int a = i, b = pos[i], c = n-a+1, d = n-b+1;

			sw(a, b);
			sw(c, d);
		}
	}
	debug(per+1, per+1+n);
	for (int i = 1;i <= n;++i)
		if (i != per[i]) {
			cout << -1 << '\n';
			return;
		}

	cout << res.size() << ' ' << res.size() << '\n';
	for (auto [a, b] : res)
		cout << a << ' ' << b << '\n';

}
signed main(){
	ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	int T;
	cin >> T;
	while (T--)
		solve();
}

Compilation message (stderr)

cat.cpp: In function 'void solve()':
cat.cpp:12:17: warning: statement has no effect [-Wunused-value]
   12 | #define DE(...) 0
      |                 ^
cat.cpp:69:2: note: in expansion of macro 'DE'
   69 |  DE(m);
      |  ^~
cat.cpp:72:8: warning: unused variable 'x' [-Wunused-variable]
   72 |    int x = per[i];
      |        ^
cat.cpp:13:20: warning: statement has no effect [-Wunused-value]
   13 | #define debug(...) 0
      |                    ^
cat.cpp:80:2: note: in expansion of macro 'debug'
   80 |  debug(per+1, per+1+n);
      |  ^~~~~

• Subtask 1: 5.25 / 15
• Subtask 2: 10 / 10
• Subtask 3: 8.75 / 25
• Subtask 4: 15 / 15
• Subtask 5: 12.25 / 35