Submission #1079936

#	Time	Username	Problem	Language	Result	Execution time	Memory
1079936		The_Blitz	Stations (IOI20_stations)	C++17	0 / 100	4 ms	944 KiB

stations

// TODO -> PONER ALGO AQUI
// amigos y no mas
// I'm in the coolest driver high
// += O(logn) ; + = O(n)
 
#include <bits/stdc++.h>
#include "stations.h"
#include <variant>
#define fastio ios_base::sync_with_stdio(0); cin.tie(0)
#define ones(x) __builtin_popcount(x)
#define loga2(x) __builtin_ctzll(x)
#define pos2(x) __builtin_clzll(x)

using namespace std;
 
typedef long long ll;
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
typedef pair <ii, ii> iiii;
typedef vector <int> vi;
typedef vector <ii> vii;

const int mod = 998244353;
const ll inf = (1LL<<62)-1;

struct HASH{
  size_t operator()(const pair<int,int>&x)const{
    return hash<long long>()(((long long)x.first)^(((long long)x.second)<<32));
  }
};

vector< vector<int> > G;
vector<int> P , H;
vector<bool> vis;
int N;

int st[1005][11];

void dfs(int x){
  for(int i=0; i<G[x].size(); i++){
    int &y = G[x][i];
    if(!vis[y]){
      vis[y] = true;
      H[y] = H[x]+1;
      P[y] = x;
      dfs(y);
    }
  }
}

void build(){
  for(int i=0 ; i<N ; i++) st[i][0] = P[i];

  for(int i=1; i<11; i++){
    for(int j=0; j<N;j++){
      st[j][i] = st[ st[j][i-1] ][i-1];
    }
  }  
}

int query(int x, int y){
  int a = x , b= y;
  if(H[a] > H[b]){
    int dis = H[a] - H[b];
    for(int i=10; i>=0; i--){
      if(dis & (1<<i) ){
        a = st[a][i];
        dis -= (1<<i);
      }
    }
  }

  else if(H[a] < H[b]){
    int dis = H[b] - H[a];
    for(int i=10; i>=0; i--){
      if(dis & (1<<i) ){
        b = st[b][i];
        dis -= (1<<i);
      }
    }
  }

  if(a==b){
    if(a==x){
      b = y;
      int dis = (H[b] - H[a]) - 1;
      for(int i=10; i>=0; i--){
        if(dis & (1<<i) ){
          b = st[b][i];
          dis -= (1<<i);
        }
      }
      return b;
    }
    else{
      return P[x];
    }
  }
  else{
    return P[x];
  }
  // s , t , P(s)
  // s <- t (BL s-1)
  // s -> t P(s)
}

vector<int> label(int n, int k, vector<int> u, vector<int> v) {
  N = n;
  vector<int> labels(n);

  for (int i = 0; i < n; i++) {
    labels[i] = i;
  }
    
  G.clear(); H.clear();
  P.clear(); vis.clear();
    
  G.resize(n);
  H.resize(n);
  P.resize(n);
  vis.resize(n,0);

  for(int i=0; i<n-1;i++){
    G[u[i]].push_back(v[i]);
    G[v[i]].push_back(u[i]);
  }

  H[0] = 0;
  P[0] = 0;
  vis[0] = true;
  dfs(0);
  build();

  return labels;
}

int find_next_station(int s, int t, std::vector<int> c) {
  cerr<<query(s,t)<<"\n";  
  return query(s,t);
}

Compilation message (stderr)

stations.cpp: In function 'void dfs(int)':
stations.cpp:40:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |   for(int i=0; i<G[x].size(); i++){
      |                ~^~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 8
• Subtask 3: 0 / 16
• Subtask 4: 0 / 10
• Subtask 5: 0 / 61