Submission #1227206

#	Time	Username	Problem	Language	Result	Execution time	Memory
1227206		brinton	Thousands Islands (IOI22_islands)	C++20	Compilation error	0 ms	0 KiB

islands

#include "islands.h"

#include <bits/stdc++.h>
using namespace std;

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
  auto co = [](int id){
    if(id%2 == 0) return id+1;
    else return id-1;
  };

  vector<set<pair<int,int>>> edges(N);// nxt,id
  for(int i = 0;i < M;i++){
    edges[U[i]].insert({V[i],i});
  }
  // if(edges[0].size() < 2) return false;
  vector<int> ans;
  vector<bool> vis(N,false);
  
  int root = 0;
  vector<int> to_root;
  while(edges[root].size() <= 1){
    if(edges[root].size() == 0) return false;
    auto [nxt,id] = *edges[root].begin();

    to_root.push_back(id);
    vis[root] = true;
    edges[root].erase({nxt,id});
    edges[nxt].erase({root,co(id)});

    root = nxt;
  }
  
  auto [nxt1,id1] = edges[root][0];
  auto [nxt2,id2] = edges[root][1];
  vector<int> ans{id1,co(id1),id2,co(id2),
                  co(id1),id1,co(id2),id2};
  
  vector<int> ret = to_root;
  for(auto &i:ans) ret.push_back(i);
  for(int i = to_root.size()-1;i >= 0;i--) ret.push_back(to_root[i]);

  return ret;
  // return ans;
}

Compilation message (stderr)

islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, std::vector<int>, std::vector<int>)':
islands.cpp:34:32: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::set<std::pair<int, int> > >, std::set<std::pair<int, int> > >::value_type' {aka 'std::set<std::pair<int, int> >'} and 'int')
   34 |   auto [nxt1,id1] = edges[root][0];
      |                                ^
islands.cpp:35:32: error: no match for 'operator[]' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::set<std::pair<int, int> > >, std::set<std::pair<int, int> > >::value_type' {aka 'std::set<std::pair<int, int> >'} and 'int')
   35 |   auto [nxt2,id2] = edges[root][1];
      |                                ^
islands.cpp:36:15: error: redeclaration of 'std::vector<int> ans'
   36 |   vector<int> ans{id1,co(id1),id2,co(id2),
      |               ^~~
islands.cpp:17:15: note: 'std::vector<int> ans' previously declared here
   17 |   vector<int> ans;
      |               ^~~