#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define rep(i,a,b) for(ll i=(ll)a;i<=(ll)b;++i)
#define all(a) a.begin(),a.end()
#define sz(x) (int)(x).size()
const int mxN = 3e3+7;
int a[mxN],b[mxN], c[mxN], mx = 0; // b = {index, wartosc}, c = {wartosc, index}
bool vis[mxN];
vector<int> cycle;
vector<pair<int,int>> pierw;
vector<pair<int,int>> drug;
void dfs(int v){
cycle.pb(v);
vis[v] = 1;
if(!vis[a[v]]) dfs(a[v]);
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n; cin >> n;
rep(i,1,n) cin >> a[i];
rep(i,1,n) b[i] = a[i];
sort(b+1,b+n+1);
rep(i,1,n) c[b[i]] = i;
rep(i,1,n) a[i] = c[a[i]];
rep(i,1,n) if(!vis[i]){
dfs(i);
mx = max(mx, sz(cycle));
int x = 0, y = sz(cycle)-1;
while(sz(cycle) > 1 && x < y){
pierw.pb({cycle[x],cycle[y]});
x++, y--;
}
cycle.clear();
}
if(mx == 1) cout << "0\n";
else if(mx == 2){
cout << "1\n";
rep(i,1,n) if(a[i] < i) drug.pb({a[i] , i});
cout << 2*sz(drug) << "\n";
for(auto [u,v] : drug) cout << u << " ";
reverse(all(drug));
for(auto [u,v] : drug) cout << v << " ";
cout << "\n";
}else{
cout << "2\n";
cout << 2*sz(pierw) << "\n";
for(auto [u,v] : pierw) cout << u << " ";
reverse(all(pierw));
for(auto [u,v] : pierw) cout << v << " ";
cout << "\n";
for(auto [u,v] : pierw) swap(a[u], a[v]);
rep(i,1,n) if(a[i] < i) drug.pb({a[i] , i});
cout << 2*sz(drug) << "\n";
for(auto [u,v] : drug) cout << u << " ";
reverse(all(drug));
for(auto [u,v] : drug) cout << v << " ";
cout << "\n";
}
}
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 | #include <bits/stdc++.h> using namespace std; typedef long long ll; typedef long double ld; #define st first #define nd second #define pb push_back #define mp make_pair #define rep(i,a,b) for(ll i=(ll)a;i<=(ll)b;++i) #define all(a) a.begin(),a.end() #define sz(x) (int)(x).size() const int mxN = 3e3+7; int a[mxN],b[mxN], c[mxN], mx = 0; // b = {index, wartosc}, c = {wartosc, index} bool vis[mxN]; vector<int> cycle; vector<pair<int,int>> pierw; vector<pair<int,int>> drug; void dfs(int v){ cycle.pb(v); vis[v] = 1; if(!vis[a[v]]) dfs(a[v]); } int main(){ ios_base::sync_with_stdio(0); cin.tie(0); int n; cin >> n; rep(i,1,n) cin >> a[i]; rep(i,1,n) b[i] = a[i]; sort(b+1,b+n+1); rep(i,1,n) c[b[i]] = i; rep(i,1,n) a[i] = c[a[i]]; rep(i,1,n) if(!vis[i]){ dfs(i); mx = max(mx, sz(cycle)); int x = 0, y = sz(cycle)-1; while(sz(cycle) > 1 && x < y){ pierw.pb({cycle[x],cycle[y]}); x++, y--; } cycle.clear(); } if(mx == 1) cout << "0\n"; else if(mx == 2){ cout << "1\n"; rep(i,1,n) if(a[i] < i) drug.pb({a[i] , i}); cout << 2*sz(drug) << "\n"; for(auto [u,v] : drug) cout << u << " "; reverse(all(drug)); for(auto [u,v] : drug) cout << v << " "; cout << "\n"; }else{ cout << "2\n"; cout << 2*sz(pierw) << "\n"; for(auto [u,v] : pierw) cout << u << " "; reverse(all(pierw)); for(auto [u,v] : pierw) cout << v << " "; cout << "\n"; for(auto [u,v] : pierw) swap(a[u], a[v]); rep(i,1,n) if(a[i] < i) drug.pb({a[i] , i}); cout << 2*sz(drug) << "\n"; for(auto [u,v] : drug) cout << u << " "; reverse(all(drug)); for(auto [u,v] : drug) cout << v << " "; cout << "\n"; } } |
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