#include "sorting.h"
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 200005;
int n, m;
int s[MAXN];
int pa[MAXN], pb[MAXN], b[MAXN];
int x[MAXN * 3], y[MAXN * 3];
vector < pair<int,int> > vres;
bool check(int k) {
vres.clear();
for (int i = 0; i < n; ++i) {
b[i] = i;
}
for (int i = 0; i < m; ++i) {
swap(b[x[i]], b[y[i]]);
}
// the swaps must satisfy: s[i] = b[i]
for (int i = 0; i < n; ++i) {
pb[s[i]] = b[i];
pa[b[i]] = s[i];
}
int cnt = 0;
for (int i = 0; i < n; ++i) {
if (pa[i] != i) {
++cnt;
// TODO: swap i, pb[i]
int j = pb[i];
vres.push_back(make_pair(i, j));
int p = pa[i], q = pa[j];
swap(pa[i], pa[j]);
pb[q] = i;
pb[p] = j;
}
}
return cnt <= k;
}
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
n = N;
m = M;
for (int i = 0; i < n; ++i) s[i] = S[i];
for (int i = 0; i < m; ++i) x[i] = X[i], y[i] = Y[i];
int low = 0, high = m;
while(low < high) {
int mid = ((low + high) >> 1);
if (check(mid)) high = mid;
else low = mid + 1;
}
check(low);
for (int i = 0; i < low; ++i) {
P[i] = vres[i].first;
Q[i] = vres[i].second;
}
return low;
}
