//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;
}
return hi==n;
}
int findSwapPairs() {
int l=0,r=m;
while (l<r) {
int mid=l+r>>1;
if (check(mid)) r = mid;
else l = mid+1;
}
assert(check(l));
return l;
}
Compilation message
sorting.cpp: In function 'int findSwapPairs()':
sorting.cpp:84:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
84 | int mid=l+r>>1;
| ~^~
/usr/bin/ld: /tmp/cc9BckmH.o: in function `main':
grader.c:(.text.startup+0x4eb): undefined reference to `findSwapPairs(int, int*, int, int*, int*, int*, int*)'
collect2: error: ld returned 1 exit status
