Language: C++

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>

using namespace std;


vector<double> x;
vector<double> y;
vector<double> r;
vector<double> c;



int main() {
  while (true) {
    int n;
    cin >> n;

    if (n == 0) {
      break;
    }

    x.resize(n);
    y.resize(n);
    r.resize(n);
    c.resize(n);

    for (int i = 0; i < n; i++) {
      cin >> x[i] >> y[i] >> r[i] >> c[i];
    }

    vector<short> dp(1 << n, 0);

    int ans = 0;

    

    
    for (int i = 0; i < (1 << n); i++) {
      int popcnt = 0;
      for (int j = 0; j < n; j++) {
        if (i & (1 << j)) {
          popcnt++;
        }
      }
      if (popcnt % 2 == 1) {
        continue;
      }
      vector<bool> tops(n, true);
      // テ」ツつづ」ツ?? jテ」ツ?ィkテ」ツ?古・ツ渉姪」ツつ古」ツつ凝」ツ?ェテ」ツつ?
      for (int a = 0; a < n; a++) {
        if (i & (1 << a)) {
          tops[a] = false;
          continue;
        }
        for (int b = a + 1; b < n; b++) {
          if (i & (1 << b)) {
            tops[b] = false;
            continue;
          }
          // iテ」ツ?ョテ」ツ?サテ」ツ??」ツ?古「ツ??
          double distance2 = pow(x[a] - x[b], 2) + pow(y[a] - y[b], 2);
          if (distance2 < pow(r[a] + r[b], 2)) {
            tops[b] = false;
          }
        }
      }
      for (int j = 0; j < n; j++) {
        for (int k = j + 1; k < n; k++) {
          if (c[j] == c[k]) {
            if (tops[j] && tops[k]) {
              // dp[i | (j, k) << c] = max(dp[i | (j, k) << c], dp[i] + 1);
              int bit = i | (1 << j) | (1 << k);
              dp[bit] = max(dp[bit], dp[i] + 1);
              ans = max(ans, dp[bit]);
            }
          }
        }
      }
    }
    
    cout << ans * 2 << endl;

  }


  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:76:28: error: no matching function for call to 'max(__gnu_cxx::__alloc_traits<std::allocator<short int>, short int>::value_type&, int)'
   76 |               dp[bit] = max(dp[bit], dp[i] + 1);
      |                         ~~~^~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 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/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:76:28: note:   deduced conflicting types for parameter 'const _Tp' ('short int' and 'int')
   76 |               dp[bit] = max(dp[bit], dp[i] + 1);
      |                         ~~~^~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:4:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:76:28: note:   mismatched types 'std::initializer_list<_Tp>' and 'short int'
   76 |               dp[bit] = max(dp[bit], dp[i] + 1);
      |                         ~~~^~~~~~~~~~~~~~~~~~~~
a.cc:77:24: error: no matching function for call to 'max(int&, __gnu_cxx::__alloc_traits<std::allocator<short int>, short int>::value_type&)'
   77 |               ans = max(ans, dp[bit]);
      |                     ~~~^~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:77:24: note:   deduced conflicting types for parameter 'const _Tp' ('int' and '__gnu_cxx::__alloc_traits<std::allocator<short int>, short int>::value_type' {aka 'short int'})
   77 |               ans = max(ans, dp[bit]);
      |                     ~~~^~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:77:24: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   77 |               ans = max(ans, dp[bit]);
      |                     ~~~^~~~~~~~~~~~~~