Submission #1057168

#	Time	Username	Problem	Language	Result	Execution time	Memory
1057168		Malix	Thousands Islands (IOI22_islands)	C++17	26 / 100	64 ms	14700 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>
#include <variant>
using namespace std;
 
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef pair<int,int> pi;
typedef vector<pi> pii;
typedef tuple<int,int,int> tii;
typedef vector<ll> li;
typedef vector<li> lii;
 
#define REP(i,a,b) for(int i=a;i<b;i++)
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define LSOne(s) ((s)&(-s))
 
ll INF=1e18+10;
int inf=1e9+10;
ll M=1e9+7;

int n,m;
vector<pii> arr;
vi vis,p,ans,ind;

void bfs(int x){
  vis[x]=1;
  int s=arr[x].size();
  if(s==1){
    ans.PB(-1);
    return;
  }
  if(s==2){
    int k=0;
    if(vis[arr[x][k].F])k++;
    ans.PB(arr[x][k].S);
    bfs(arr[x][k].F);
    if(ans.back()==-1)return;
    ans.PB(arr[x][k].S);
    return;
  }
  int k=0;
  if(vis[arr[x][k].F])k++;
  int z=arr[x][k].S;
  int y=-1;
  for(auto u:arr[arr[x][k].F])if(u.F==x)y=u.S;
  k++;
  while(vis[arr[x][k].F])k++;
  int c=arr[x][k].S;
  int d=-1;
  for(auto u:arr[arr[x][k].F])if(u.F==x&&u.S!=y)d=u.S;
  ans.PB(z);ans.PB(y);ans.PB(c);ans.PB(d);ans.PB(y);ans.PB(z);ans.PB(d);ans.PB(c);
  return;
}

int dfs(int x){
  vis[x]=1;ind.PB(x);
  for(auto u:arr[x]){
    if(vis[u.F]){
      ind.PB(u.F);
      return u.F;
    }
    p[u.F]=x;
    int k=dfs(u.F);
    if(k!=-1)return k;
  }
  ind.pop_back();
  return -1;
}

std::variant<bool, std::vector<int>> find_journey(
    int N, int M, std::vector<int> U, std::vector<int> V) {
  n=N;m=M;
  map<pi,int> mp,mp2;
  REP(i,0,m){
    mp[{U[i],V[i]}]=i;
    i++;
    mp2[{U[i],V[i]}]=i;
  }
  if(n==2){
    if(m<=2)return false;
    vi a;
    REP(i,0,m)if(U[i]==0)a.PB(i);
    int p=-1;
    REP(i,0,m)if(U[i]!=0)p=i;
    int k=a.size();
    if(k<2||p==-1)return false;
    ans.PB(a[0]);ans.PB(p);ans.PB(a[1]);ans.PB(a[0]);ans.PB(p);ans.PB(a[1]);
    return ans;
  }

  
if(m>2&&U[0]==U[1]){
  arr.resize(n);
  REP(i,0,m){
    arr[U[i]].PB({V[i],i});
    i++;
  }
  vis.resize(n,0);
  p.resize(n,-1);
  vis[0]=1;int k=-1;
  ind.PB(0);
  for(auto u:arr[0]){
    p[u.F]=0;
    k=dfs(u.F);
    if(k!=-1)break;
  }
  if(k==-1)return false;
  int pos=0;
  vi a;
  while(ind[pos]!=k){
    a.PB(mp[{ind[pos],ind[pos+1]}]);
    ans.PB(mp[{ind[pos],ind[pos+1]}]);
    pos++;
  }
  vi tmp;
  int z=ind.size();
  REP(i,pos,z-1)tmp.PB(ind[i]);
  z=tmp.size();vi b,c;
  REP(i,0,z-1){
    b.PB(mp[{tmp[i],tmp[i+1]}]);
    ans.PB(mp[{tmp[i],tmp[i+1]}]);
  }
  b.PB(mp[{tmp[z-1],tmp[0]}]);
  ans.PB(mp[{tmp[z-1],tmp[0]}]);
  REP(i,0,z-1){
    c.PB(mp2[{tmp[i],tmp[i+1]}]);
    ans.PB(mp2[{tmp[i],tmp[i+1]}]);
  }
  c.PB(mp2[{tmp[z-1],tmp[0]}]);
  ans.PB(mp2[{tmp[z-1],tmp[0]}]);
  reverse(b.begin(),b.end());
  reverse(c.begin(),c.end());
  for(auto u:b)ans.PB(u);
  for(auto u:c)ans.PB(u);

  reverse(a.begin(),a.end());
  for(auto u:a)ans.PB(u);
  return ans;
}

  arr.resize(n);
  REP(i,0,m)arr[U[i]].PB({V[i],i});
  if(arr[0].size()>=2){
    int x=arr[0][0].S;
    int y=-1;
    for(auto u:arr[arr[0][0].F])if(u.F==0)y=u.S;
    int c=arr[0][1].S;
    int d=-1;
    for(auto u:arr[arr[0][1].F])if(u.F==0)d=u.S;
    ans.PB(x);ans.PB(y);ans.PB(c);ans.PB(d);ans.PB(y);ans.PB(x);ans.PB(d);ans.PB(c);
    return ans;
  }
  if(arr[0].empty())return false;
  vis.resize(n,0);
  vis[0]=1;
  ans.PB(arr[0][0].S);
  bfs(arr[0][0].F);
  if(ans.back()==-1)return false;
  ans.PB(arr[0][0].S);
  return ans;
}

• Subtask 1: 5 / 5
• Subtask 2: 0 / 5
• Subtask 3: 21 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45