Language: C++

#include<iostream>
#include<cmath>
#include<numeric>
#include<functional>
#include<string>
#include<algorithm>
#include<vector>
#include<map>
#include<iomanip>
#define rep(i,n) for(int i=0;i<n;i++)
#define rep1(i,n) for(int i=1;i<n;i++)
#define ll long long
using namespace std;

int main(){
  string s;
  cin>>s;
  int n=s.length();
  int mod=2019;
  int rui10[200020];
  rui10[0]=1;
  for(int i=1;i<200020;i++){
    rui10[i]=(10*rui10[i-1])%mod;
  }
  int x[n+1];
  x[0]=0; x[1]=stoi(s[n-1]);
  for(int i=2;i<=n;i++){
    x[i]=(x[i-1]+stoi(s[n-i])*rui10[i-1])%mod;
  }
  map<int,ll> mp;
  ll ans=0;
  rep(i,n+1){
    mp[x[i]]++;
  }
  for(auto p:mp){
    ans+=p.second*(p.second-1)/2;
  }
  cout<<ans;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:26:20: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   26 |   x[0]=0; x[1]=stoi(s[n-1]);
      |                ~~~~^~~~~~~~
In file included from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~
a.cc:28:22: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   28 |     x[i]=(x[i-1]+stoi(s[n-i])*rui10[i-1])%mod;
      |                  ~~~~^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~