Language: C++

#include<iostream>
#include<cstdlib>
#include<vector>
#include<queue>
#include<cstring>

using namespace std;

int table[100000][3] = {};

int main(){
  int n,m;
  cin >> n >> m;
  vector<vector<int> > edge(n);
  for(int i = 0;i < m;i++){
    int a,b;
    cin >> a >> b;
    a--;
    b--;
    edge[a].push_back(b);
    edge[b].push_back(a);
  }
  int s,t;
  cin >> s >> t;
  s--;
  t--;
  memset(table,-1,sizeof(table));
  queue<vector<int> > q;
  q.push(vector<int> {s,0});
  table[s][0] = 0;
  int flag = 1;
  while(q.size() && flag){
    vector<int> temp = q.front();
    q.pop();
    for(int i = 0;i < edge[temp].size();i++){
      int dist = table[temp[0]][temp[1]];
      int st = dist%3;
      if(table[edge[temp][i]][st] == -1){
        table[edge[temp][i]][st] = dist;
        q.push(vector<int>{edge[temp][i],st});
      }
      if(edge[temp][i] == t && st == 0){
        flag = 0;
      }
    }
  }
  if(flag){
    cout << -1 << endl;
  }else{
    cout << table[t][0] << endl;
  }
  return 0;
}
  
  

Compiler output:
a.cc: In function 'int main()':
a.cc:35:27: error: no match for 'operator[]' (operand types are 'std::vector<std::vector<int> >' and 'std::vector<int>')
   35 |     for(int i = 0;i < edge[temp].size();i++){
      |                           ^
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:3:
/usr/include/c++/14/bits/stl_vector.h:1128:7: note: candidate: 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; reference = std::vector<int>&; size_type = long unsigned int]'
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1128:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1147:7: note: candidate: 'std::vector<_Tp, _Alloc>::const_reference std::vector<_Tp, _Alloc>::operator[](size_type) const [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; const_reference = const std::vector<int>&; size_type = long unsigned int]'
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1147:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
a.cc:38:20: error: no match for 'operator[]' (operand types are 'std::vector<std::vector<int> >' and 'std::vector<int>')
   38 |       if(table[edge[temp][i]][st] == -1){
      |                    ^
/usr/include/c++/14/bits/stl_vector.h:1128:7: note: candidate: 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; reference = std::vector<int>&; size_type = long unsigned int]'
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1128:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1147:7: note: candidate: 'std::vector<_Tp, _Alloc>::const_reference std::vector<_Tp, _Alloc>::operator[](size_type) const [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; const_reference = const std::vector<int>&; size_type = long unsigned int]'
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1147:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
a.cc:39:19: error: no match for 'operator[]' (operand types are 'std::vector<std::vector<int> >' and 'std::vector<int>')
   39 |         table[edge[temp][i]][st] = dist;
      |                   ^
/usr/include/c++/14/bits/stl_vector.h:1128:7: note: candidate: 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; reference = std::vector<int>&; size_type = long unsigned int]'
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1128:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1147:7: note: candidate: 'std::vector<_Tp, _Alloc>::const_reference std::vector<_Tp, _Alloc>::operator[](size_type) const [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; const_reference = const std::vector<int>&; size_type = long unsigned int]'
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1147:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
a.cc:40:32: error: no match for 'operator[]' (operand types are 'std::vector<std::vector<int> >' and 'std::vector<int>')
   40 |         q.push(vector<int>{edge[temp][i],st});
      |                                ^
/usr/include/c++/14/bits/stl_vector.h:1128:7: note: candidate: 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; reference = std::vector<int>&; size_type = long unsigned int]'
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1128:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1147:7: note: candidate: 'std::vector<_Tp, _Alloc>::const_reference std::vector<_Tp, _Alloc>::operator[](size_type) const [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; const_reference = const std::vector<int>&; size_type = long unsigned int]'
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1147:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
a.cc:40:44: error: no matching function for call to 'std::vector<int>::vector(<brace-enclosed initializer list>)'
   40 |         q.push(vector<int>{edge[temp][i],st});
      |                                            ^
/usr/include/c++/14/bits/stl_vector.h:707:9: note: candidate: 'template<class _InputIterator, class> std::vector<_Tp, _Alloc>::vector(_InputIterator, _InputIterator, const allocator_type&) [with <template-parameter-2-2> = _InputIterator; _Tp = int; _Alloc = std::allocator<int>]'
  707 |         vector(_InputIterator __first, _InputIterator __last,
      |         ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:707:9: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/stl_vector.h:678:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::initializer_list<_Tp>, const allocator_type&) [with _Tp = int; _Alloc = std::allocator<int>; allocator_type = std::allocator<int>]'
  678 |       vector(initializer_list<value_type> __l,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:678:7: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/14/bits/stl_vector.h:659:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, std::__type_identity_t<_Alloc>&) [with _Tp = int; _Alloc = std::allocator<int>; std::__type_identity_t<_Alloc> = std::allocator<int>]'
  659 |       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:659:7: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/14/bits/stl_vector.h:640:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, const allocator_type&, std::false_type) [with _Tp = int; _Alloc = std::allocator<int>; allocator_type = std::allocator<int>; std::false_type = std::false_type]'
  640 |       vector(vector&& __rv, const allocator_type& __m, false_type)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:640:7: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_vector.h:635:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, const allocator_type&, std::true_type) [with _Tp = int; _Alloc = std::allocator<int>; allocator_type = std::allocator<int>; std::true_type = std::true_type]'
  635 |       vector(vector&& __rv, const allocator_type& __m, true_type) noexcept
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:635:7: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_vector.h:624:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&, std::__type_identity_t<_Alloc>&) [with _Tp = int; _Alloc = std::allocator<int>; std::__type_identity_t<_Alloc> = std::allocator<int>]'
  624 |       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:624:7: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/14/bits/stl_vector.h:620:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&) [with _Tp = int; _Alloc = std::allocator<int>]'
  620 |       vector(vector&&) noexcept = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:620:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:601:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = int; _Alloc = std::allocator<int>]'
  601 |       vector(const vector& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:601:7: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_vector.h:569:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(size_type, const value_type&, const allocator_type&) [with _Tp = int; _Alloc = std::allocator<int>; size_type = long unsigned int; value_type = int; allocator_type = std::allocator<int>]'
  569 |