#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], ma[MAX_N];
void fail() {
puts("-1"), exit(0);
}
void sw(int a, int 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);
reverse(AI(R));
if (m&1)
return false;
for (int i = 0;i < m;++i)
if (L[i] != rev(R[i]))
return false;
for (int i = 0;i < m;++i) {
swap(per[L[i]], per[R[i]]);
ma[L[i]] = R[i];
}
// 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);
vector<vector<int>> loop;
int ex = 0, ones = 0;
for (int i = 1;i <= m;++i) {
if (per[i] == i && !ma[i]) continue;
vector<int> child;
while (i != per[i]) {
int x = per[i];
child.pb(x);
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);
}
child.pb(i);
loop.pb(child);
int cnt = 0;
for (int u : child) cnt += !ma[u];
ex += cnt >> 1;
ones += cnt&1;
}
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() - ex + max(0, ones - 1) << '\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
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:13:20: warning: statement has no effect [-Wunused-value]
13 | #define debug(...) 0
| ^
cat.cpp:93:2: note: in expansion of macro 'debug'
93 | debug(per+1, per+1+n);
| ^~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
646 ms |
262148 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
3 ms |
384 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
646 ms |
262148 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
3 ms |
384 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
646 ms |
262148 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
