#include<bits/stdc++.h>
#define FOR(i,a,b) for(int i=a;i<(int)b;++i)
#define FORD(i,a,b) for(int i=a;i>=(int)b;--i)
#define PB push_back
#define EB emplace_back
#define FI first
#define SE second
#define umap unordered_map
#define uset unordered_set
#define vi vector<int>
#define vvi vector<vi>
#define vll vector<ll>
#define vvll vector<vll>
#define vpii vector<pii>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ALL(X) (X).begin(),(X).end()
#ifndef DEBUG
#define endl (char)10
#endif
using namespace std;
using ll = long long;
using ld = long double;
template <class T>
istream& operator>> (istream& is, vector<T>& vec){
FOR(i,0,vec.size()) is >> vec[i];
return is;
}
template <class T>
ostream& operator<< (ostream& os, vector<T>& vec){
for(auto& t : vec) os << t << " ";
return os;
}
template<class T, class U>
ostream& operator<< (ostream& os, const pair<T, U>& p){
os << p.FI << " " << p.SE;
return os;
}
template<class T, class U>
istream& operator>> (istream& is, pair<T, U>& p){
is >> p.FI >> p.SE;
return is;
}
vvi cycles(vi& p){
vvi res;
int n = p.size();
FOR(i,0,n){
// if(p[i] >= 0){ // odkomentowac dla cykli dl. 1
if(p[i] >= 0 && p[i] != i){
res.PB({});
int t = i, tv;
while(p[t] >= 0){
res.back().PB(t);
tv = t;
t = p[t];
p[tv] = -p[tv] - 1;
}
}
}
FOR(i,0,n) if (i != p[i]) p[i] = -p[i] - 1;
return res;
}
void solve(vi& V, vector<vpii>& sol){
vpii round;
vvi C = cycles(V);
for(auto& c : C){
if (c.size() == 2){
round.EB(c[0], c[1]);
} else {
FOR(i,1,c.size()){
int j = c.size() - i;
if (j <= i) break;
round.EB(c[i], c[j]);
}
}
}
if (!round.empty()){
FOR(i,0,round.size()){
swap(V[round[i].FI], V[round[i].SE]);
round[i].FI++;
round[i].SE++;
}
sol.PB(round);
//exit(0);
solve(V, sol);
}
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n;
vi V(n);
cin >> V;
vi vals(ALL(V));
sort(ALL(vals));
FOR(i,0,n) V[i] = lower_bound(ALL(vals), V[i]) - vals.begin();
vector<vpii> sol;
solve(V, sol);
cout << sol.size() << endl;
for(auto& v : sol){
cout << 2 * v.size() << endl;
FOR(i,0,v.size()) cout << v[i].FI << " ";
FORD(i,v.size()-1,0) cout << v[i].SE << " ";
cout << endl;
}
}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 | #include<bits/stdc++.h> #define FOR(i,a,b) for(int i=a;i<(int)b;++i) #define FORD(i,a,b) for(int i=a;i>=(int)b;--i) #define PB push_back #define EB emplace_back #define FI first #define SE second #define umap unordered_map #define uset unordered_set #define vi vector<int> #define vvi vector<vi> #define vll vector<ll> #define vvll vector<vll> #define vpii vector<pii> #define pii pair<int, int> #define pll pair<ll, ll> #define ALL(X) (X).begin(),(X).end() #ifndef DEBUG #define endl (char)10 #endif using namespace std; using ll = long long; using ld = long double; template <class T> istream& operator>> (istream& is, vector<T>& vec){ FOR(i,0,vec.size()) is >> vec[i]; return is; } template <class T> ostream& operator<< (ostream& os, vector<T>& vec){ for(auto& t : vec) os << t << " "; return os; } template<class T, class U> ostream& operator<< (ostream& os, const pair<T, U>& p){ os << p.FI << " " << p.SE; return os; } template<class T, class U> istream& operator>> (istream& is, pair<T, U>& p){ is >> p.FI >> p.SE; return is; } vvi cycles(vi& p){ vvi res; int n = p.size(); FOR(i,0,n){ // if(p[i] >= 0){ // odkomentowac dla cykli dl. 1 if(p[i] >= 0 && p[i] != i){ res.PB({}); int t = i, tv; while(p[t] >= 0){ res.back().PB(t); tv = t; t = p[t]; p[tv] = -p[tv] - 1; } } } FOR(i,0,n) if (i != p[i]) p[i] = -p[i] - 1; return res; } void solve(vi& V, vector<vpii>& sol){ vpii round; vvi C = cycles(V); for(auto& c : C){ if (c.size() == 2){ round.EB(c[0], c[1]); } else { FOR(i,1,c.size()){ int j = c.size() - i; if (j <= i) break; round.EB(c[i], c[j]); } } } if (!round.empty()){ FOR(i,0,round.size()){ swap(V[round[i].FI], V[round[i].SE]); round[i].FI++; round[i].SE++; } sol.PB(round); //exit(0); solve(V, sol); } } int main () { ios_base::sync_with_stdio(false); cin.tie(0); int n; cin >> n; vi V(n); cin >> V; vi vals(ALL(V)); sort(ALL(vals)); FOR(i,0,n) V[i] = lower_bound(ALL(vals), V[i]) - vals.begin(); vector<vpii> sol; solve(V, sol); cout << sol.size() << endl; for(auto& v : sol){ cout << 2 * v.size() << endl; FOR(i,0,v.size()) cout << v[i].FI << " "; FORD(i,v.size()-1,0) cout << v[i].SE << " "; cout << endl; } } |
English