Submission #597681

#	Time	Username	Problem	Language	Result	Execution time	Memory
597681		codebuster_10	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	385 ms	43756 KiB

oneway

#include <bits/stdc++.h>
#define int int64_t //be careful about this 

using namespace std;

#define vt vector 
#define ar array 
#define pr pair 

#define f first 
#define s second

#define pb push_back
#define eb emplace_back

#define fr(i,a,b) for(int i = (a); i < (b); ++i)
#define rf(i,a,b) for(int i = (b)-1; i >= (a); --i)
#define all(x) x.begin(),x.end()
#define mem(a,b) memset(a,b,sizeof(a))

namespace IN{
  template<class T> void re(vector<T> &A);
  template<class S,class T> void re(pair<S,T> &A);
  template<class T,size_t N> void re(array<T,N> &A);

  template<class T> void re(T& x){ 
    cin >> x;}
  template<class H, class... T> void re(H& h, T&... t){ 
    re(h); re(t...);}

  template<class T> void re(vector<T> &A){ 
    for(auto& x : A) re(x);}
  template<class S,class T> void re(pair<S,T> &A){ 
      re(A.first); re(A.second);}
  template<class T,size_t N> void re(array<T,N> &A){
    for(int i = 0; i < N; ++i)  re(A[i]);}
}

namespace OUT{
  template<class T>
  void __p(const T& a){ cout<<a; }
  template<class T, class F>
  void __p(const pair<T, F>& a){ cout<<"{"; __p(a.first); cout<<","; __p(a.second); cout<<"}\n"; }
  template<class T, size_t N>
  void __p(const array<T,N>& a){ cout<<"{"; for(int i=0;i<N;++i)__p(a[i]),cout<<",}\n"[i+1==N]; }
  template<class T>
  void __p(const vector<T>& a){
    cout<<"{";for(auto it=a.begin();it<a.end();it++)__p(*it),cout<<",}\n"[it+1==a.end()]; }
  template<class T, class ...Arg>
  void __p(T a1, Arg ...a){__p(a1); __p(a...); }
  template<class Arg1>
  void __f(const char *s, Arg1 &&arg1){ cout<<s<<" : "; __p(arg1); cout<<endl; }
  template<class Arg1, class ... Args>
  void __f(const char *ss, Arg1 &&arg1, Args &&... args){
    int b=0,i=0; do{ if(ss[i]=='(') b++; if(ss[i]==')') b--; i++;}while(!(ss[i]==','&&b==0));
    const char *comma=ss+i; cout.write(ss,comma-ss)<<" : ";__p(arg1);cout<<" | ";__f(comma+1,args...);}
  #define trace(...) cout<<"Line:"<<__LINE__<<"  ", __f(#__VA_ARGS__, __VA_ARGS__)
}


namespace FUNC{
  void IO(string s = ""){
    ios_base::sync_with_stdio(NULL); 
    cin.tie(nullptr); 
    cout.precision(20); 
    cout << fixed;
    if(!s.empty()){
      freopen((s+".in").c_str(),"r",stdin);
      freopen((s+".out").c_str(),"w",stdout);
    }
  }

  const auto start_time = chrono::high_resolution_clock::now();
  void output_run_time(){
    // will work for ac,cc&&cf.
#ifndef ONLINE_JUDGE
    auto end_time = chrono::high_resolution_clock::now();
    chrono::duration<double> diff = end_time-start_time;
      cout << "\n\n\nTime Taken : " << diff.count();
#endif
  }

  template<class T> bool ckmin(T& a, const T& b){ 
    return b < a ? a = b, true : false; }
    
  template<class T> bool ckmax(T& a, const T& b){ 
    return a < b ? a = b, true : false; }

  mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
  int my_rand(int L, int R){ 
    return uniform_int_distribution<int>(L,R)(rng); }
  
  template<class T> int sz(const T& x){ 
    return int(x.size()); }

  template<class T> int lb(const vector<T>& vec,const T& val){
    return int(lower_bound(vec.begin(), vec.end(),val) - vec.begin()); }

  template<class T> int ub(const vector<T>& vec,const T& val){
    return int(upper_bound(vec.begin(), vec.end(),val) - vec.begin()); }

  constexpr int  dx[4] = {1,0,-1,0};
  constexpr int  dy[4] = {0,1,0,-1};
  constexpr char dr[4] = {'D','R','U','L'};

  constexpr long long INFLL1 = 1e16, INFLL2 = 9e18;
  constexpr int INF = 2e9;

  template<class T>
  vector<T> V(int n,T val){
    return vector<T> (n,val);
  }

  template<class T>
  vector<vector<T>> V(int n,int m,T val){
    return vector<vector<T>> (n,vector<T> (m,val));
  }

  template<class T>
  vector<vector<vector<T>>> V(int n,int m,int k,T val){
    return vector<vector<vector<T>>> (n,vector<vector<T>> (m,vector<T> (k,val)));
  }
}


using namespace IN;
using namespace OUT;
using namespace FUNC;












struct DSU {
  int n, z;
  // root node: -1 * component size
  // otherwise: parent
  vector<int> parent_or_size;

  DSU(int n_ = -1){
    if(n_ >= 0)
      init(n_);
  }

  void init(int n_){
    z = n = n_;
    parent_or_size.assign(n_, -1);
  } 

  bool merge(int a, int b){
    int x = leader(a), y = leader(b);
    if(x == y) 
      return false;
    if(-parent_or_size[x] < -parent_or_size[y]) 
      swap(x, y);
    parent_or_size[x] += parent_or_size[y];
    parent_or_size[y] = x;
    z--;
    return true;
  }

  bool same(int a, int b){
    return leader(a) == leader(b);
  }

  int leader(int a){
    if(parent_or_size[a] < 0) 
      return a;
    return parent_or_size[a] = leader(parent_or_size[a]);
  }

  int size(int a){
    return -parent_or_size[leader(a)];
  }
  
  vector<vector<int>> groups(){
    vector<int> leader_buf(n), group_size(n);
    for(int i = 0; i < n; i++){
      leader_buf[i] = leader(i);
      group_size[leader_buf[i]]++;
    }
    vector<vector<int>> result(n);
    for(int i = 0; i < n; i++){
      result[i].reserve(group_size[i]);
    }
    for(int i = 0; i < n; i++){
      result[leader_buf[i]].push_back(i);
    }
    result.erase(remove_if(result.begin(), result.end(),[&](const auto& v){return v.empty(); }),result.end());
    return result;
  }

  int comp(){
    return z;
  }
};

vt<pr<int,int>> bridges;
DSU dsu;


vector<vector<int>> two_edge_cc(const vector<vector<int>>& g_){

  struct E{
    int to,id;
  };

  int n = g_.size();

  vector<vector<E>> g(n);

  for(int i = 0, f = 0; i < n; ++i)
    for(auto j : g_[i])
      if(j < i){
        g[j].push_back({i,f});
        g[i].push_back({j,f++});
      }
    

  vector<int> depth(n,-1), up(n);
  dsu.init(n);

  auto dfs = [&](auto self,int node,int parent_id) -> bool {
    up[node] = depth[node];
    for(auto [child,id] : g[node])
      if(id != parent_id)
        if(depth[child] < 0){
          depth[child] = depth[node] + 1;
          if(!self(self,child,id)){
            dsu.merge(node,child);
          }else{
            bridges.pb({node,child});
          }
          up[node] = min(up[node],up[child]);
        }else{
          up[node] = min(up[node],depth[child]);
        }
      
    return up[node] == depth[node];
  }; 

  for(int i = 0; i < n; ++i)
    if(depth[i] < 0){
      depth[i] = 0;
      dfs(dfs,i,-1);
    }

  return dsu.groups();
}







signed main(){
  IO();

  int n,m;
  re(n,m);

  vt<vt<int>> g(n);
  vt<pr<int,int>> edges;
  fr(e,0,m){
    int u,v; re(u,v); --u,--v;
    edges.push_back({u,v});
    g[u].pb(v);
    g[v].pb(u);
  }

  two_edge_cc(g);

  vt<vt<int>> tree(n);

  set<pr<int,int>> chk;

  for(auto [u,v] : bridges){
    u = dsu.leader(u);
    v = dsu.leader(v);
    tree[u].pb(v);
    tree[v].pb(u);
    chk.insert({u,v});
  }

  int k;
  re(k);

  vt<int> val(n,0);

  while(k--){
    int u,v; re(u,v); --u,--v;
    u = dsu.leader(u);
    v = dsu.leader(v);
    val[u]++;
    val[v]--;
  }

  set<pr<int,int>> dir;

  vt<bool> vis(n,false);

  auto dfs = [&](auto self,int i,int parent) -> void {
    vis[i] = true;
    for(auto j : tree[i])
      if(j != parent){
        self(self,j,i);
        val[i] += val[j];
        if(val[j] > 0){
          dir.insert({j,i});
        }else if(val[j] < 0){
          dir.insert({i,j});
        }
      }
  };

  fr(i,0,n) if(!vis[dsu.leader(i)]) dfs(dfs,dsu.leader(i),-1);

  for(auto [u,v] : edges){
    int pu = dsu.leader(u), pv = dsu.leader(v);
    if(pu == pv){
      cout << "B";
    }else{
      assert(chk.count({pu,pv}) || chk.count({pv,pu}));
      if(dir.count({pu,pv})){
        cout << "R";
      }else if(dir.count({pv,pu})){
        cout << "L";
      }else{
        cout << "B";
      }
    }
  }
  


  // output_run_time();
  return 0;
}

Compilation message (stderr)

oneway.cpp: In lambda function:
oneway.cpp:233:9: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
  233 |       if(id != parent_id)
      |         ^
oneway.cpp: In function 'void FUNC::IO(std::string)':
oneway.cpp:68:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |       freopen((s+".in").c_str(),"r",stdin);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:69:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   69 |       freopen((s+".out").c_str(),"w",stdout);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40