843A

 843A - Sorting by Subsequences

还好之前了解过一点白书上的permutation！

我写的递归，其实很容易直接写成递推啊

#include <bits/stdc++.h>
using namespace std;
const int maxn=1e5+10;
int res;
int nex[maxn];
struct Node{
    int id,x;
    bool operator<(const Node &a)const {
        return x<a.x;
    }
}p[maxn];
int vis[maxn];
vector<int> v[maxn];
void dfs(int u){
    vis[u]=1;
    v[res].push_back(u);
    if(!vis[nex[u]]) dfs(nex[u]);
}
int main(){
    int n;
    while(scanf("%d",&n)!=EOF){
        res=0;
        for(int i=0;i<=n;i++) v[i].clear();
        for(int i=1;i<=n;i++){
            scanf("%d",&p[i].x);
            p[i].id=i;
        }
        sort(p+1,p+n+1);
        for(int i=1;i<=n;i++){
            nex[i]=p[i].id;
        }
        memset(vis,0,sizeof(vis));
        for(int i=1;i<=n;i++) if(!vis[i]){
            dfs(i);
            res++;
        }
        printf("%d
",res);
        for(int i=0;i<res;i++){
            printf("%d",v[i].size());
            for(int j=0;j<v[i].size();j++) printf(" %d",v[i][j]);
            puts("");
        }
    }
}

tourist~~

#include <bits/stdc++.h>

using namespace std;

const int N = 1234567;

pair <int, int> a[N];
int p[N];
bool was[N];

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d", &a[i].first);
    a[i].second = i;
  }
  sort(a, a + n);
  for (int i = 0; i < n; i++) {
    p[i] = a[i].second;
  }
  vector < vector <int> > res;
  for (int i = 0; i < n; i++) {
    if (was[i]) {
      continue;
    }
    int x = i;
    vector <int> cycle;
    while (!was[x]) {
      was[x] = true;
      cycle.push_back(x);
      x = p[x];
    }
    res.push_back(cycle);
  }
  int cnt = res.size();
  printf("%d
", cnt);
  for (int i = 0; i < cnt; i++) {
    int cc = res[i].size();
    printf("%d", cc);
    for (int j = 0; j < cc; j++) {
      printf(" %d", res[i][j] + 1);
    }
    printf("
");
  }
  return 0;
}