#include "sorting.h"
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
random_device(rd);
mt19937 rng(rd());
const long long FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
struct custom_hash
{
template<class T>
unsigned long long operator()(T v) const
{
unsigned long long x = v;
x += FIXED_RANDOM; x += 11400714819323198485ull;
x = (x ^ (x >> 30)) * 13787848793156543929ull;
x = (x ^ (x >> 27)) * 10723151780598845931ull;
return x ^ (x >> 31);
}
};
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T, class U> using hash_table = gp_hash_table<T, U, custom_hash>;
template<class T>
void ckmin(T &a, T b)
{
a = min(a, b);
}
template<class T>
void ckmax(T &a, T b)
{
a = max(a, b);
}
long long expo(long long a, long long e, long long mod)
{
return ((e == 0) ? 1 : ((expo(a * a % mod, e >> 1, mod)) * ((e & 1) ? a : 1) % mod));
}
template<class T, class U>
T nmod(T &x, U mod)
{
if (x >= mod) x -= mod;
}
template<class T>
T gcd(T a, T b)
{
return (b ? gcd(b, a % b) : a);
}
template<class T>
T randomize(T mod)
{
return (uniform_int_distribution<T>(0, mod - 1))(rng);
}
#define y0 ___y0
#define y1 ___y1
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define PF push_front
#define fi first
#define se second
#define DBG(x) cerr << #x << " = " << x << endl;
#define SZ(x) ((int) (x.size()))
#define FOR(i, a, b) for (auto i = (a); i < (b); i++)
#define FORD(i, a, b) for (auto i = (a) - 1; i >= (b); i--)
#define ALL(x) x.begin(), x.end()
const long double PI = 4.0 * atan(1.0);
const long double EPS = 1e-9;
#define MAGIC 347
#define SINF 10007
#define CO 1000007
#define INF 1000000007
#define BIG 1000000931
#define LARGE 1696969696967ll
#define GIANT 2564008813937411ll
#define LLINF 2696969696969696969ll
#define MAXN 600013
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pdd;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<ld> vd;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
typedef vector<pdd> vpd;
int N, M;
int arr[MAXN];
pii swp[MAXN];
vpi ans;
int ord[MAXN], rord[MAXN], val[MAXN], pos[MAXN];
void sw(int p, int q, bool flag)
{
//POSITION p, q!
swap(val[p], val[q]);
swap(pos[val[p]], pos[val[q]]);
if (!flag)
{
swap(rord[p], rord[q]);
swap(ord[rord[p]], ord[rord[q]]);
}
else
{
ans.PB({p, q});
}
// cerr << "state:\n";
// FOR(i, 0, N)
// {
// cerr << rord[i] << ' ';
// }
// cerr << endl;
// FOR(i, 0, N)
// {
// cerr << val[i] << ' ';
// }
// cerr << endl;
// cerr << p << ' ' << q << endl;
}
bool check(int x)
{
FOR(i, 0, N)
{
ord[i] = i;
rord[i] = i;
val[i] = arr[i];
pos[arr[i]] = i;
}
FORD(i, x, 0)
{
//ord: a[i] = x => the one that will end up at position i is currently at x
//rord: a[i] = x => the one that is currently at i will end up at position x
pii p = swp[i];
swap(rord[p.fi], rord[p.se]);
swap(ord[rord[p.fi]], ord[rord[p.se]]);
}
// cerr << "state:\n";
// FOR(i, 0, N)
// {
// cerr << rord[i] << ' ';
// }
// cerr << endl;
// FOR(i, 0, N)
// {
// cerr << arr[i] << ' ';
// }
// cerr << endl;
// FOR(i, 0, N)
// {
// cerr << ord[i] << ' ';
// }
// cerr << endl;
ans.clear();
int iter = 0;
FOR(i, 0, x)
{
pii p = swp[i];
sw(p.fi, p.se, 0);
while (iter < N && rord[pos[iter]] == iter)
{
iter++;
}
// DBG(iter);
if (iter == N)
{
int x = randomize(N);
ans.PB({x, x});
continue;
}
sw(pos[iter], ord[iter], 1);
}
return (iter == N);
}
int findSwapPairs(int n, int s[], int m, int x[], int y[], int p[], int q[])
{
N = n;
FOR(i, 0, N)
{
arr[i] = s[i];
}
M = m;
FOR(i, 0, M)
{
swp[i] = {x[i], y[i]};
}
check(3);
FOR(i, 0, SZ(ans))
{
p[i] = ans[i].fi;
q[i] = ans[i].se;
}
return SZ(ans);
int lo = 0, hi = M;
while(hi > lo)
{
int mid = (hi + lo) >> 1;
if (check(mid))
{
hi = mid;
}
else
{
lo = mid + 1;
}
}
check(lo);
FOR(i, 0, SZ(ans))
{
p[i] = ans[i].fi;
q[i] = ans[i].se;
}
return SZ(ans);
}
