#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 kout() {cerr << endl;}
template<class T1, class ...T2>
void kout (T1 v, T2 ...e) { cerr << v << ' ', kout(e...); }
template<class T>
void debug(T L, T R) { while (L != R) cerr << *L << " \n"[next(L)==R], ++L; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 300010;
int n;
vector<pair<int,int>> op;
// just the front half
void swap_sort(vector<int> p) {
}
bool valid(vector<int> p) {
int cnt = 0, m = n / 2;
for (int l = 0, r = n-1;l < r;++l, --r) {
if ((p[l]>m) ^ (p[r]<=m))
return false;
if (p[l] > m)
++cnt;
}
if (cnt & 1)
return false;
vector<int> pos(n);
for (int i = 0;i < n;++i)
pos[ p[i] ] = i;
auto sw = [&](int x, int y) {
swap(p[x], p[y]), swap(pos[ p[x] ], pos[ p[y] ]);
};
auto do_op = [&](int x, int y) {
int a = x, b = y, c = n - x - 1, d = n - y - 1;
sw(a, b), sw(c, d);
};
for (int i = 0;i < m;++i) {
while (i+1 != p[i])
do_op(i, p[i]);
}
for (int i = 0;i < n;++i)
if (p[i] != i+1)
return false;
return true;
}
// make p good enough so that I can do swap sort on it
void pair_good(vector<int> &p) {
}
bool solve() {
cin >> n;
vector<int> p(n);
for (int &i : p)
cin >> i;
if (!valid(p))
return false;
pair_good(p);
swap_sort(p);
return true;
}
signed main() {
ios_base::sync_with_stdio(0), cin.tie(0);
int T;
cin >> T;
while (T--) {
op.clear();
if (!solve())
cout << -1 << '\n';
else {
cout << op.size() << ' ' << op.size() << '\n';
for (auto [a, b] : op)
cout << a+1 << ' ' << b+1 << '\n';
}
}
}
#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 kout() {cerr << endl;}
template<class T1, class ...T2>
void kout (T1 v, T2 ...e) { cerr << v << ' ', kout(e...); }
template<class T>
void debug(T L, T R) { while (L != R) cerr << *L << " \n"[next(L)==R], ++L; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 300010;
int n;
vector<pair<int,int>> op;
// just the front half
void swap_sort(vector<int> p) {
}
bool valid(vector<int> p) {
int cnt = 0, m = n / 2;
for (int l = 0, r = n-1;l < r;++l, --r) {
if ((p[l]>m) ^ (p[r]<=m))
return false;
if (p[l] > m)
++cnt;
}
if (cnt & 1)
return false;
vector<int> pos(n);
for (int i = 0;i < n;++i)
pos[ p[i] ] = i;
auto sw = [&](int x, int y) {
swap(p[x], p[y]), swap(pos[ p[x] ], pos[ p[y] ]);
};
auto do_op = [&](int x, int y) {
int a = x, b = y, c = n - x - 1, d = n - y - 1;
sw(a, b), sw(c, d);
};
for (int i = 0;i < m;++i) {
while (i+1 != p[i])
do_op(i, p[i]);
}
for (int i = 0;i < n;++i)
if (p[i] != i+1)
return false;
return true;
}
// make p good enough so that I can do swap sort on it
void pair_good(vector<int> &p) {
}
bool solve() {
cin >> n;
vector<int> p(n);
for (int &i : p)
cin >> i;
if (!valid(p))
return false;
pair_good(p);
swap_sort(p);
return true;
}
signed main() {
ios_base::sync_with_stdio(0), cin.tie(0);
int T;
cin >> T;
while (T--) {
op.clear();
if (!solve())
cout << -1 << '\n';
else {
cout << op.size() << ' ' << op.size() << '\n';
for (auto [a, b] : op)
cout << a+1 << ' ' << b+1 << '\n';
}
}
}
Compilation message
cat.cpp:97:11: error: redefinition of 'const int MAX_N'
97 | const int MAX_N = 300010;
| ^~~~~
cat.cpp:17:11: note: 'const int MAX_N' previously defined here
17 | const int MAX_N = 300010;
| ^~~~~
cat.cpp:98:5: error: redefinition of 'int n'
98 | int n;
| ^
cat.cpp:18:5: note: 'int n' previously declared here
18 | int n;
| ^
cat.cpp:99:23: error: redefinition of 'std::vector<std::pair<int, int> > op'
99 | vector<pair<int,int>> op;
| ^~
cat.cpp:19:23: note: 'std::vector<std::pair<int, int> > op' previously declared here
19 | vector<pair<int,int>> op;
| ^~
cat.cpp:101:6: error: redefinition of 'void swap_sort(std::vector<int>)'
101 | void swap_sort(vector<int> p) {
| ^~~~~~~~~
cat.cpp:21:6: note: 'void swap_sort(std::vector<int>)' previously defined here
21 | void swap_sort(vector<int> p) {
| ^~~~~~~~~
cat.cpp:103:6: error: redefinition of 'bool valid(std::vector<int>)'
103 | bool valid(vector<int> p) {
| ^~~~~
cat.cpp:23:6: note: 'bool valid(std::vector<int>)' previously defined here
23 | bool valid(vector<int> p) {
| ^~~~~
cat.cpp:133:6: error: redefinition of 'void pair_good(std::vector<int>&)'
133 | void pair_good(vector<int> &p) {
| ^~~~~~~~~
cat.cpp:53:6: note: 'void pair_good(std::vector<int>&)' previously defined here
53 | void pair_good(vector<int> &p) {
| ^~~~~~~~~
cat.cpp:135:6: error: redefinition of 'bool solve()'
135 | bool solve() {
| ^~~~~
cat.cpp:55:6: note: 'bool solve()' previously defined here
55 | bool solve() {
| ^~~~~
cat.cpp:146:8: error: redefinition of 'int main()'
146 | signed main() {
| ^~~~
cat.cpp:66:8: note: 'int main()' previously defined here
66 | signed main() {
| ^~~~
