//by szh
#include<bits/stdc++.h>
#include <unordered_map>
using namespace std;
#define fi first
#define se second
#define pii pair<int,int>
#define pll pair<long long,long long>
#define pb push_back
#define debug(x) cerr<<#x<<"="<<x<<endl
#define pq priority_queue
#define inf 0x3f
#define rep(i,a,b) for (int i=a;i<(b);i++)
#define MP make_pair
#define SZ(x) (int(x.size()))
#define ll long long
#define mod 1000000007
#define ALL(x) x.begin(),x.end()
void inc(int &a,int b) {a=(a+b)%mod;}
void dec(int &a,int b) {a=(a-b+mod)%mod;}
int lowbit(int x) {return x&(-x);}
ll p0w(ll base,ll p) {ll ret=1;while(p>0){if (p%2ll==1ll) ret=ret*base%mod;base=base*base%mod;p/=2ll;}return ret;}
#include "sorting.h"
const int maxn = 6e5+10;
int n,m;
int a[maxn],b[maxn];
pii ans[maxn];
pii p[maxn];
deque <int> q[maxn];
int id[maxn];
pii pos[maxn];
pii qid[maxn];
bool check(int cnt) {
rep(i,0,n) {
while (!q[i].empty()) q[i].pop_back();
q[i].pb(i);
id[i] = i;
b[i] = a[i];
}
rep(i,0,cnt) {
int x=p[i].fi,y=p[i].se;
if (x==y) continue;
q[id[x]].pb(y);
q[id[y]].pb(x);
swap(id[x],id[y]);
qid[i] = {id[x],id[y]};
}
rep(i,0,n) {
pos[q[i].back()].fi = q[i].front();
pos[a[i]].se = i;
}
int hi = 0;
rep(i,0,cnt) {
int x = p[i].fi,y=p[i].se;
if (x!=y) {
swap(b[x],b[y]);
pos[b[x]].se = x,pos[b[y]].se = y;
q[qid[i].fi].pop_front(),q[qid[i].se].pop_front();
pos[q[qid[i].fi].back()].fi = q[qid[i].fi].front();
pos[q[qid[i].se].back()].fi = q[qid[i].se].front();
}
pii cur = {0,0};
while (hi<n and pos[hi].fi==pos[hi].se) hi++;
if (hi<n) cur = pos[hi];
x = cur.fi,y=cur.se;
if (x!=y) {
swap(b[x],b[y]);
pos[b[x]].se = x,pos[b[y]].se = y;
}
ans[i] = cur;
}
while (hi<n and pos[hi].fi==pos[hi].se) hi++;
return hi==n;
}
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
n = N,m= M;
int l=0,r=M;
rep(i,0,n) a[i] =S[i];
rep(i,0,M) p[i] = {X[i],Y[i]};
while (l<r) {
int mid=l+r>>1;
if (check(mid)) r = mid;
else l = mid+1;
}
assert(check(l));
rep(i,0,l) P[i] = ans[i].fi, Q[i] = ans[i].se;
return l;
}
int main()
{
int N, M;
scanf("%d",&N);
int S[233],X[233],Y[233],P[233],Q[233];
for (int i = 0; i < N; ++i)
scanf("%d",&S[i]);
scanf("%d",&M);
for (int i = 0; i < M; ++i) {
scanf("%d%d",&X[i],&Y[i]);
}
int ans = findSwapPairs(N, S, M, X, Y, P, Q);
printf("%d\n", ans);
for (int i = 0; i < ans; ++i)
printf("%d %d\n", P[i], Q[i]);
return 0;
}
Compilation message
sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:89:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
89 | int mid=l+r>>1;
| ~^~
sorting.cpp: In function 'int main()':
sorting.cpp:109:6: warning: declaration of 'ans' shadows a global declaration [-Wshadow]
109 | int ans = findSwapPairs(N, S, M, X, Y, P, Q);
| ^~~
sorting.cpp:32:5: note: shadowed declaration is here
32 | pii ans[maxn];
| ^~~
sorting.cpp:101:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
101 | scanf("%d",&N);
| ~~~~~^~~~~~~~~
sorting.cpp:104:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
104 | scanf("%d",&S[i]);
| ~~~~~^~~~~~~~~~~~
sorting.cpp:105:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
105 | scanf("%d",&M);
| ~~~~~^~~~~~~~~
sorting.cpp:107:11: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
107 | scanf("%d%d",&X[i],&Y[i]);
| ~~~~~^~~~~~~~~~~~~~~~~~~~
/usr/bin/ld: /tmp/ccY2Y95s.o: in function `main':
grader.c:(.text.startup+0x0): multiple definition of `main'; /tmp/ccxFj31r.o:sorting.cpp:(.text.startup+0x0): first defined here
collect2: error: ld returned 1 exit status
