Language: C++

#include<bits/stdc++.h>
using namespace std;
#define ll long long int
const int mod=1e9+7;
ll index;

void add_self(ll& a,ll b){
    a+=b;
    if(a>=mod)
        a%=mod;
}

vector<vector<ll>> mul(vector<vector<ll>> a,vector<vector<ll>> b){
    vector<vector<ll>> res(index,vector<ll>(index));

    for(int i=0;i<index;i++){
        for(int j=0;j<index;j++){
            for(int k=0;k<index;k++){
                res[i][k]+=(a[i][j]*b[j][k])%mod;
                res[i][k]%=mod;
            }
        }
    }
    return res;
}

int main()
{
    ll n,k;
    cin>>n>>k;
    index=n;
    vector<vector<ll>>edges (n,vector<ll>(n));
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++)
            cin>>edges[i][j];
    }
    vector<vector<ll>> res(n,vector<ll>(n));
    for(int i=0;i<n;i++) res[i][i]=1;
     while(k){
        if(k%2) res=mul(res,edges);
          edges=mul(edges,edges);
        k/=2;
     }
    ll answer=0;
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
        add_self(answer,res[i][j]);
        }
    }
    cout<<answer;

}


Compiler output:
a.cc:5:4: error: 'long long int index' redeclared as different kind of entity
    5 | ll index;
      |    ^~~~~
In file included from /usr/include/string.h:462,
                 from /usr/include/c++/14/cstring:43,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:121,
                 from a.cc:1:
/usr/include/strings.h:50:20: note: previous declaration 'const char* index(const char*, int)'
   50 | extern const char *index (const char *__s, int __c)
      |                    ^~~~~
a.cc: In function 'std::vector<std::vector<long long int> > mul(std::vector<std::vector<long long int> >, std::vector<std::vector<long long int> >)':
a.cc:14:50: error: no matching function for call to 'std::vector<long long int>::vector(<unresolved overloaded function type>)'
   14 |     vector<vector<ll>> res(index,vector<ll>(index));
      |                                                  ^
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53:
/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 = long long int; _Alloc = std::allocator<long long int>]'
  707 |         vector(_InputIterator __first, _InputIterator __last,
      |         ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:707:9: note:   candidate expects 2 arguments, 1 provided
/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 = long long int; _Alloc = std::allocator<long long int>; allocator_type = std::allocator<long long int>]'
  678 |       vector(initializer_list<value_type> __l,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:678:43: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::initializer_list<long long int>'
  678 |       vector(initializer_list<value_type> __l,
      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/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 = long long int; _Alloc = std::allocator<long long int>; std::__type_identity_t<_Alloc> = std::allocator<long long int>]'
  659 |       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:659:7: note:   candidate expects 2 arguments, 1 provided
/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 = long long int; _Alloc = std::allocator<long long int>; allocator_type = std::allocator<long long 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, 1 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 = long long int; _Alloc = std::allocator<long long int>; allocator_type = std::allocator<long long 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, 1 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 = long long int; _Alloc = std::allocator<long long int>; std::__type_identity_t<_Alloc> = std::allocator<long long int>]'
  624 |       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:624:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:620:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&) [with _Tp = long long int; _Alloc = std::allocator<long long int>]'
  620 |       vector(vector&&) noexcept = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:620:14: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<long long int>&&'
  620 |       vector(vector&&) noexcept = default;
      |              ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:601:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = long long int; _Alloc = std::allocator<long long int>]'
  601 |       vector(const vector& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:601:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'const std::vector<long long int>&'
  601 |       vector(const vector& __x)
      |              ~~~~~~~~~~~~~~^~~
/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 = long long int; _Alloc = std::allocator<long long int>; size_type = long unsigned int; value_type = long long int; allocator_type = std::allocator<long long int>]'
  569 |       vector(size_type __n, const value_type& __value,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:569:7: note:   candidate expects 3 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:556:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(size_type, const allocator_type&) [with _Tp = long long int; _Alloc = std::allocator<long long int>; size_type = long unsigned int; allocator_type = std::allocator<long long int>]'
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:556:24: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<long long int>::size_type' {aka 'long unsigned int'}
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |              ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:542:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const allocator_type&) [with _Tp = long long int; _Alloc = std::allocator<long long int>; allocator_type = std::allocator<long long int>]'
  542 |       vector(const allocator_type& __a) _GLIBCXX_NOEXCEPT
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:542:36: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'const std::vector<long long int>::allocator_type&' {aka 'const std::allocator<long long int>&'}
  542 |       vector(const allocator_type& __a) _GLIBCXX_NOEXCEPT
      |              ~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector() [with _Tp = long long int; _Alloc = std::allocator<long long int>]'
  531 |       vector() = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note:   candidate expects 0 arguments, 1 provided
a.cc:16:18: error: invalid operands of types 'int' and '<unresolved overloaded function type>' to binary 'operator<'
   16 |     for(int i=0;i<index;i++){
      |                 ~^~~~~~
a.cc:17:22: error: invalid operands of types 'int' and '<unresolved overloaded function type>' to binary 'operator<'
   17 |         for(int j=0;j<index;j++){
      |                     ~^~~~~~
a.cc:18:26: error: invalid operands of types 'int' and '<unresolved overloaded function type>' to binary 'operator<'
   18 |             for(int k=0;k<index;k++){
      |                         ~^~~~~~
a.cc: In function 'int main()':
a.cc:31:11: error: overloaded function with no contextual type information
   31 |     index=n;
      |           ^