#include <bits/stdc++.h>
#define f first
#define s second
#define pb push_back
#define vec vector
#define sz(x) (int)x.size()
using namespace std;
typedef pair<int,int> pii;
auto rng=bind(uniform_int_distribution<int>(1,1e9),mt19937(time(0)));
signed main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
int t;
cin>>t;
while(t--){
int n;
cin>>n;
vec<int> a(n);
for(auto &z : a) cin>>z,z--;
vec<pii>vc;
auto do_op=[&](int i,int j){
vc.pb({i,j});
swap(a[i],a[j]);swap(a[n-i-1],a[n-j-1]);
};
// for(int i=0;i)
int ok=1;
map<pii,int>mp;
for(int i=0;i<n/2;i++){
ok&=(a[i]==n-a[n-i-1]-1);
if(a[i]!=i && a[n-i-1]!=i){
if(a[i]<a[n-i-1]) mp[{a[i],a[n-i-1]}]=i;
else mp[{a[n-i-1],a[i]}]=n-i-1;
}
}
if(!ok){
cout<<-1<<'\n';
continue;
}
auto print=[&](){
cout<<"ARR "<<endl;
for(auto &z : a) cout<<z<<' ';
cout<<endl;
};
for(int i=0;i<n/2;i++){
if(a[i]!=i && a[n-i-1]!=i){
// cerr<<"WHA "<<i<<' '<<n-i-1<<endl;
// assert(mp.count({i,n-i-1}));
int j=mp[{i,n-i-1}];
do_op(i,j);
// cout<<"SWAP "<<i+1<<' '<<j+1<<endl;
// print();
if(a[j]<a[n-j-1])mp[{a[j],a[n-j-1]}]=j;
else mp[{a[n-j-1],a[j]}]=j;
}
}
vec<int>bad;
for(int i=0;i<n/2;i++){
if(a[i]!=i){
if(a[n-i-1]!=i) assert(false);
bad.pb(i);
}
}
if(sz(bad)%2){
cout<<-1<<'\n';
continue;
}
for(int i=0;i<sz(bad);i+=2){
int x=bad[i],y=bad[i+1];
do_op(x,n-y-1);
do_op(x,y);
}
for(int i=0;i<n;i++) ok&=(a[i]==i);
if(!ok) cout<<-1<<'\n';
else{
cout<<sz(vc)<<' '<<sz(vc)<<'\n';
for(auto &z : vc)
cout<<z.f+1<<' '<<z.s+1<<'\n';
}
}
return 0;
}
Compilation message
cat.cpp: In function 'int main()':
cat.cpp:40:14: warning: variable 'print' set but not used [-Wunused-but-set-variable]
40 | auto print=[&](){
| ^~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Partially correct |
8 ms |
332 KB |
Valid reconstruction |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
32 ms |
968 KB |
Output is correct |
2 |
Correct |
33 ms |
968 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Partially correct |
8 ms |
332 KB |
Valid reconstruction |
2 |
Correct |
32 ms |
968 KB |
Output is correct |
3 |
Correct |
33 ms |
968 KB |
Output is correct |
4 |
Partially correct |
35 ms |
1092 KB |
Valid reconstruction |
5 |
Partially correct |
14 ms |
588 KB |
Valid reconstruction |
6 |
Partially correct |
12 ms |
588 KB |
Valid reconstruction |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
32 ms |
968 KB |
Output is correct |
2 |
Correct |
33 ms |
968 KB |
Output is correct |
3 |
Execution timed out |
1084 ms |
28684 KB |
Time limit exceeded |
4 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Partially correct |
8 ms |
332 KB |
Valid reconstruction |
2 |
Correct |
32 ms |
968 KB |
Output is correct |
3 |
Correct |
33 ms |
968 KB |
Output is correct |
4 |
Partially correct |
35 ms |
1092 KB |
Valid reconstruction |
5 |
Partially correct |
14 ms |
588 KB |
Valid reconstruction |
6 |
Partially correct |
12 ms |
588 KB |
Valid reconstruction |
7 |
Execution timed out |
1084 ms |
28684 KB |
Time limit exceeded |
8 |
Halted |
0 ms |
0 KB |
- |