#ifndef CPL_TEMPLATE
#define CPL_TEMPLATE
/*
Normie's Template v2.5
Changes:
Added warning against using pragmas on USACO.
*/
// Standard library in one include.
#include <bits/stdc++.h>
using namespace std;
// ordered_set library.
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ordered_set(el) tree<el,null_type,less<el>,rb_tree_tag,tree_order_statistics_node_update>
// AtCoder library. (Comment out these two lines if you're not submitting in AtCoder.) (Or if you want to use it in other judges, run expander.py first.)
//#include <atcoder/all>
//using namespace atcoder;
//Pragmas (Comment out these three lines if you're submitting in szkopul or USACO.)
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast,unroll-loops,tree-vectorize")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
//File I/O.
#define FILE_IN "cseq.inp"
#define FILE_OUT "cseq.out"
#define ofile freopen(FILE_IN,"r",stdin);freopen(FILE_OUT,"w",stdout)
//Fast I/O.
#define fio ios::sync_with_stdio(0);cin.tie(0)
#define nfio cin.tie(0)
#define endl "\n"
//Order checking.
#define ord(a,b,c) ((a>=b)and(b>=c))
//min/max redefines, so i dont have to resolve annoying compile errors.
#define min(a,b) (((a)<(b))?(a):(b))
#define max(a,b) (((a)>(b))?(a):(b))
// Fast min/max assigns to use with AVX.
// Requires g++ 9.2.0.
template<typename T>
__attribute__((always_inline)) void chkmin(T& a, const T& b) {
a=(a<b)?a:b;
}
template<typename T>
__attribute__((always_inline)) void chkmax(T& a, const T& b) {
a=(a>b)?a:b;
}
//Constants.
#define MOD (ll(998244353))
#define MAX 300001
#define mag 320
const long double PI=3.14159265358979;
//Pairs and 3-pairs.
#define p1 first
#define p2 second.first
#define p3 second.second
#define fi first
#define se second
#define pii(element_type) pair<element_type,element_type>
#define piii(element_type) pair<element_type,pii(element_type)>
//Quick power of 2.
#define pow2(x) (ll(1)<<x)
//Short for-loops.
#define ff(i,__,___) for(int i=__;i<=___;i++)
#define rr(i,__,___) for(int i=__;i>=___;i--)
//Typedefs.
#define bi BigInt
typedef long long ll;
typedef long double ld;
typedef short sh;
// Binpow and stuff
ll BOW(ll a, ll x, ll p)
{
if (!x) return 1;
ll res=BOW(a,x/2,p);
res*=res;
res%=p;
if (x%2) res*=a;
return res%p;
}
ll INV(ll a, ll p)
{
return BOW(a,p-2,p);
}
//---------END-------//
#endif
vector<int> vec;
vector<pii(int)> seq;
int n,m,i,j,k,t,t1,u,v,a,b;
int arr[200001];
int brr[100001];
int crr[100001];
int used[100001];
int main()
{
fio;
cin>>t;
for (t1=0;t1<t;t1++) {
cin>>n;
seq.clear();
for (i=1;i<=n;i++) {
cin>>arr[i];
}
for (i=1;i<=n/2;i++) if (arr[i]+arr[n+1-i] != n+1) {
cout<<-1<<endl;
break;
}
if (i<=n/2) {
continue;
}
for (i=1;i<=n/2;i++) {
if (arr[i]<=n/2) {
crr[arr[i]]=0;
brr[arr[i]]=i;
} else {
crr[n+1-arr[i]]=1;
brr[n+1-arr[i]]=i;
}
used[i]=0;
}
for (i=1;i<=n/2;i++) if (!used[i]) {
u=i;
vec.clear();
while(true) {
used[u]=1;
vec.push_back(u);
u=brr[u];
if (used[u]) break;
}
for (j=1;j<vec.size();j++) {
u=vec[0];
v=vec[j];
if (crr[v]) {
crr[u]^=1;
crr[v]^=1;
seq.push_back({brr[u],n+1-brr[v]});
} else {
seq.push_back({brr[u],brr[v]});
}
swap(brr[u],brr[v]);
}
}
vec.clear();
for (i=1;i<=n/2;i++) if (crr[i]) {
vec.push_back(i);
}
if (vec.size()%2) {
cout<<-1<<endl;
continue;
} else {
for (i=0;i<vec.size();i+=2) {
u=vec[i];
v=vec[i+1];
seq.push_back({brr[u],brr[v]});
seq.push_back({brr[u],n+1-brr[v]});
}
}
cout<<seq.size()<<' '<<seq.size()<<endl;
for (auto g : seq) {
cout<<g.fi<<' '<<g.se<<endl;
}
}
}
// Normie28;
/*
abcd
badc
dcba
cdab
*/
Compilation message
cat.cpp:23: warning: ignoring '#pragma comment ' [-Wunknown-pragmas]
23 | #pragma comment(linker, "/stack:200000000")
|
cat.cpp: In function 'int main()':
cat.cpp:144:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
144 | for (j=1;j<vec.size();j++) {
| ~^~~~~~~~~~~
cat.cpp:165:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
165 | for (i=0;i<vec.size();i+=2) {
| ~^~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
332 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
24 ms |
1016 KB |
Output is correct |
| 2 |
Correct |
24 ms |
972 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
332 KB |
Output is correct |
| 2 |
Correct |
24 ms |
1016 KB |
Output is correct |
| 3 |
Correct |
24 ms |
972 KB |
Output is correct |
| 4 |
Correct |
27 ms |
1016 KB |
Output is correct |
| 5 |
Correct |
10 ms |
596 KB |
Output is correct |
| 6 |
Correct |
8 ms |
588 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
24 ms |
1016 KB |
Output is correct |
| 2 |
Correct |
24 ms |
972 KB |
Output is correct |
| 3 |
Correct |
538 ms |
28316 KB |
Output is correct |
| 4 |
Correct |
500 ms |
27500 KB |
Output is correct |
| 5 |
Correct |
549 ms |
30328 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
332 KB |
Output is correct |
| 2 |
Correct |
24 ms |
1016 KB |
Output is correct |
| 3 |
Correct |
24 ms |
972 KB |
Output is correct |
| 4 |
Correct |
27 ms |
1016 KB |
Output is correct |
| 5 |
Correct |
10 ms |
596 KB |
Output is correct |
| 6 |
Correct |
8 ms |
588 KB |
Output is correct |
| 7 |
Correct |
538 ms |
28316 KB |
Output is correct |
| 8 |
Correct |
500 ms |
27500 KB |
Output is correct |
| 9 |
Correct |
549 ms |
30328 KB |
Output is correct |
| 10 |
Correct |
535 ms |
25208 KB |
Output is correct |
| 11 |
Correct |
485 ms |
23552 KB |
Output is correct |
| 12 |
Correct |
538 ms |
28724 KB |
Output is correct |
| 13 |
Correct |
563 ms |
29632 KB |
Output is correct |
| 14 |
Correct |
515 ms |
28400 KB |
Output is correct |
