Submission #1060361

#	Time	Username	Problem	Language	Result	Execution time	Memory
1060361		mychecksedad	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	863 ms	1272 KiB

longesttrip

#include "longesttrip.h"
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define all(x) x.begin(),x.end()
#define ll long long
#define ff first
#define ss second
#define vi vector<int>
const int N = 200005;
 
std::vector<int> longest_trip(int n, int D)
{
  if(D == 3){
    vector<int> v;
    for(int i = 0; i < n; ++i) v.pb(i);
    return v;
  }
  if(D == 2){
    deque<int> v;
    v.pb(0);
    int o = -1;
    for(int i = 1; i < n; ++i){
      bool x = are_connected(vi{0}, vi{i});
      if(x){
        o = i;
        v.pb(i);
        break;
      }
    }
    if(o == -1){
      vi res;
      for(int i = 1; i < n; ++i){
        res.pb(i);
      }
      return res;
    }
    for(int i = 1; i < n; ++i){
      if(o == i) continue;
      bool x = are_connected(vi{v[0]}, vi{i});
      if(x){
        v.push_front(i);
      }else v.pb(i);
    }
    vector<int> res(all(v));
    return res;
  }
  vector<vector<int>> g(n);
  vector<vector<bool>> is(n, vector<bool>(n));
  for(int i = 0; i < n; ++i){
    for(int j = i + 1; j < n; ++j){
      bool ok = are_connected(vi{i}, vi{j});
      if(ok){
        is[i][j] = is[j][i] = 1;
        g[i].pb(j);
        g[j].pb(i);
      }
    }
  }
  vector<vector<int>> S;
  for(int i = 0; i < n; ++i){
    if(g[i].empty()){
      vi res;
      for(int j = 0; j < n; ++j){
        if(j != i) res.pb(j);
      }
      return res;
    }
    bool okk = 0;
    for(auto &s: S){
      bool ok = 1;
      for(int x: s){
        if(is[x][i] == 0) ok = 0;
      }
      if(ok == 1){
        s.pb(i);
        okk = 1;
        break;
      }
    }
    if(okk == 0){
      S.pb(vi{i});
    }
  }
  if(S.size() == 1) return S[0];
  if(S.size() == 2){
    for(int &x: S[0]){
      for(int &y: S[1]){
        if(is[x][y]){
          swap(x, S[0].back());
          swap(y, S[1][0]);
          vi res;
          for(int f: S[0]) res.pb(f);
          for(int f: S[1]) res.pb(f);
          return res;
        }   
      }
    }
    if(S[0].size() > S[1].size()) return S[0];
    return S[1];
  }
  
  deque<int> a, b;
  a.pb(0);
  for(int i = 1; i < n; ++i){
    if(is[a[0]][i]){
      a.push_front(i);
    }else if(is[a.back()][i]){
      a.pb(i);
    }else{
      if(b.empty()) b.pb(i);
      else{
        if(is[b[0]][i]){
          b.push_front(i);
        }else if(is[b.back()][i]){
          b.pb(i);
        }else{
          if(is[a.back()][b[0]]){
            for(int x: b) a.pb(x);
            b.clear();
            b.pb(i);
          }else{
            assert(false);
          }
        }
      }
    }
  }
  if(b.size()>a.size())swap(a,b);

  int u = -1, v;

  while(a.size() < n){
    if(is[a[0]][a.back()] == 0){
      if(is[a[0]][b.back()] == 1){
        a.push_front(b.back());
        b.pop_back();
      }else{
        a.pb(b.back());
        b.pop_back();
      }
    }else{
      if(u == -1){
        for(int i = 0; i < a.size(); ++i){
          for(int j = i + 1; j < a.size(); ++j){
            if(is[u][v] == 0){
              u = a[i], v = a[j];
              break;
            }
          }
          if(u != -1) break;
        }
      }
      assert(u != -1);
      assert(b.size());
      if(is[b.back()][u] == 1){
        while(a.front() != u){
          int x = a.front();
          a.pop_front();
          a.pb(x);
        }
        a.push_front(b.back());
        b.pop_back();
      }else{
        while(a.front() != v){
          int x = a.front();
          a.pop_front();
          a.pb(x);
        }
        a.push_front(b.back());
        b.pop_back();
      }
    }
  }
  vi res(all(a));
  return res;
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:133:18: warning: comparison of integer expressions of different signedness: 'std::deque<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  133 |   while(a.size() < n){
      |         ~~~~~~~~~^~~
longesttrip.cpp:144:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::deque<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  144 |         for(int i = 0; i < a.size(); ++i){
      |                        ~~^~~~~~~~~~
longesttrip.cpp:145:32: warning: comparison of integer expressions of different signedness: 'int' and 'std::deque<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  145 |           for(int j = i + 1; j < a.size(); ++j){
      |                              ~~^~~~~~~~~~
longesttrip.cpp:146:23: warning: 'v' may be used uninitialized in this function [-Wmaybe-uninitialized]
  146 |             if(is[u][v] == 0){
      |                       ^

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 60