Submission #236126

#	Time	Username	Problem	Language	Result	Execution time	Memory
236126		VEGAnn	Retro (COCI17_retro)	C++14	Compilation error	0 ms	0 KiB

retro

#include <bits/stdc++.h>
#define sz(x) ((int)x.size())
#define a3 array<int, 3>
using namespace std;
const int N = 310;
const int oo = 2e9;
string ans = "", f[2][N][N], t;
char s[N][N];
int n, m, ff[2][N][N], an = 0;

bool better(string &nw, string &old){
    return (sz(nw) > sz(old) || (sz(nw) == sz(old) && nw < old));
}

void upd(int &x, int y){
    x = max(x, y);
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);

#ifdef _LOCAL
    freopen("in.txt","r",stdin);
#endif // _LOCAL

    cin >> n >> m;

    for (int i = 0; i < n; i++)
    for (int j = 0; j < m; j++)
        cin >> s[n - 1 - i][j];

    if (n > 100) {
        for (int j = 0; j < m; j++)
            if (s[0][j] == 'M')
                ff[0][j][0] = 0;
            else ff[0][j][0] = -1;

        for (int i = 0, tp = 0; i < n - 1; i++, tp ^= 1){
            for (int j = 0; j < m; j++)
            for (int sm = 0; sm <= i + 1; sm++)
                ff[tp ^ 1][j][sm] = -1;

            for (int j = 0; j < m; j++)
            for (int sm = 0; sm <= i; sm++){
                if (ff[tp][j][sm] == -1) continue;

                for (int stp = -1; stp < 2; stp++){
                    int ni = i + 1, nj = j + stp;

                    if (nj < 0 || nj >= m) continue;

                    if (s[ni][nj] == '*'){
                        if (sm == 0){
                            an = max(an, ff[tp][j][sm]);
                        }
                    } else if (s[ni][nj] == '.'){
                        upd(ff[tp ^ 1][nj][sm], ff[tp][j][sm]);
                    } else if (s[ni][nj] == '('){
                        upd(ff[tp ^ 1][nj][sm + 1], ff[tp][j][sm + 1]);
                    } else if (s[ni][nj] == ')'){
                        if (sm == 0) continue;

                        upd(ff[tp ^ 1][nj][sm - 1], ff[tp][j][sm + 1]);
                    }
                }
            }
        }

        int tp = (n - 1) % 2;

        for (int j = 0; j < m; j++)
            upd(an, ff[tp][j][0]);

        cout << an << '\n';

        for (int i = 0; i < ans; i++)
            cout << "(";
    } else {
        for (int j = 0; j < m; j++)
            if (s[0][j] == 'M')
                f[0][j][0] = "";
            else f[0][j][0] = ")";

        for (int i = 0, tp = 0; i < n - 1; i++, tp ^= 1){
            for (int j = 0; j < m; j++)
            for (int sm = 0; sm <= i + 1; sm++)
                f[tp ^ 1][j][sm] = ")";

            for (int j = 0; j < m; j++)
            for (int sm = 0; sm <= i; sm++){
                if (f[tp][j][sm] == ")") continue;

                for (int stp = -1; stp < 2; stp++){
                    int ni = i + 1, nj = j + stp;

                    if (nj < 0 || nj >= m) continue;

                    if (s[ni][nj] == '*'){
                        if (sm == 0){
                            if (better(f[tp][j][sm], ans))
                                ans = f[tp][j][sm];
                        }
                    } else if (s[ni][nj] == '.'){
                        if (f[tp ^ 1][nj][sm] == ")" || better(f[tp][j][sm], f[tp ^ 1][nj][sm]))
                            f[tp ^ 1][nj][sm] = f[tp][j][sm];
                    } else if (s[ni][nj] == '('){
                        t = f[tp][j][sm] + "(";

                        if (f[tp ^ 1][nj][sm + 1] == ")" || better(t, f[tp ^ 1][nj][sm + 1]))
                            f[tp ^ 1][nj][sm + 1] = t;
                    } else if (s[ni][nj] == ')'){
                        if (sm == 0) continue;

                        t = f[tp][j][sm] + ")";

    //                    cerr << t << '\n' << f[tp ^ 1][nj][sm - 1] << '\n';

                        if (f[tp ^ 1][nj][sm - 1] == ")" || better(t, f[tp ^ 1][nj][sm - 1]))
                            f[tp ^ 1][nj][sm - 1] = t;
                    }
                }
            }
        }

        int tp = (n - 1) % 2;

        for (int j = 0; j < m; j++)
            if (f[tp][j][0] != ")" && better(f[tp][j][0], ans))
                ans = f[tp][j][0];
    }

    cout << sz(ans) << '\n' << ans;

    return 0;
}

Compilation message (stderr)

retro.cpp: In function 'int main()':
retro.cpp:76:27: error: no match for 'operator<' (operand types are 'int' and 'std::__cxx11::string {aka std::__cxx11::basic_string<char>}')
         for (int i = 0; i < ans; i++)
                         ~~^~~~~
In file included from /usr/include/c++/7/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:110,
                 from retro.cpp:1:
/usr/include/c++/7/bits/regex.h:962:5: note: candidate: template<class _BiIter> bool std::__cxx11::operator<(const std::__cxx11::sub_match<_BiIter>&, const std::__cxx11::sub_match<_BiIter>&)
     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
     ^~~~~~~~
/usr/include/c++/7/bits/regex.h:962:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:110,
                 from retro.cpp:1:
/usr/include/c++/7/bits/regex.h:1041:5: note: candidate: template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const std::__cxx11::sub_match<_BiIter>&)
     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
     ^~~~~~~~
/usr/include/c++/7/bits/regex.h:1041:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:110,
                 from retro.cpp:1:
/usr/include/c++/7/bits/regex.h:1121:5: note: candidate: template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(const std::__cxx11::sub_match<_BiIter>&, std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)
     operator<(const sub_match<_Bi_iter>& __lhs,
     ^~~~~~~~
/usr/include/c++/7/bits/regex.h:1121:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:110,
                 from retro.cpp:1:
/usr/include/c++/7/bits/regex.h:1198:5: note: candidate: template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const std::__cxx11::sub_match<_BiIter>&)
     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
     ^~~~~~~~
/usr/include/c++/7/bits/regex.h:1198:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:110,
                 from retro.cpp:1:
/usr/include/c++/7/bits/regex.h:1272:5: note: candidate: template<class _Bi_iter> bool std::__cxx11::operator<(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)
     operator<(const sub_match<_Bi_iter>& __lhs,
     ^~~~~~~~
/usr/include/c++/7/bits/regex.h:1272:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:110,
                 from retro.cpp:1:
/usr/include/c++/7/bits/regex.h:1349:5: note: candidate: template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const std::__cxx11::sub_match<_BiIter>&)
     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
     ^~~~~~~~
/usr/include/c++/7/bits/regex.h:1349:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:110,
                 from retro.cpp:1:
/usr/include/c++/7/bits/regex.h:1429:5: note: candidate: template<class _Bi_iter> bool std::__cxx11::operator<(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)
     operator<(const sub_match<_Bi_iter>& __lhs,
     ^~~~~~~~
/usr/include/c++/7/bits/regex.h:1429:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/future:39:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:105,
                 from retro.cpp:1:
/usr/include/c++/7/thread:281:3: note: candidate: bool std::operator<(std::thread::id, std::thread::id)
   operator<(thread::id __x, thread::id __y) noexcept
   ^~~~~~~~
/usr/include/c++/7/thread:281:3: note:   no known conversion for argument 1 from 'int' to 'std::thread::id'
In file included from /usr/include/c++/7/forward_list:38:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:104,
                 from retro.cpp:1:
/usr/include/c++/7/bits/forward_list.h:1391:5: note: candidate: template<class _Tp, class _Alloc> bool std::operator<(const std::forward_list<_Tp, _Alloc>&, const std::forward_list<_Tp, _Alloc>&)
     operator<(const forward_list<_Tp, _Alloc>& __lx,
     ^~~~~~~~
/usr/include/c++/7/bits/forward_list.h:1391:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::forward_list<_Tp, _Alloc>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0,
                 from retro.cpp:1:
/usr/include/c++/7/valarray:1186:1: note: candidate: template<class _Tp> std::_Expr<std::_BinClos<std::__less, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__less, _Tp>::result_type> std::operator<(const _Tp&, const std::valarray<_Tp>&)
 _DEFINE_BINARY_OPERATOR(<, __less)
 ^
/usr/include/c++/7/valarray:1186:1: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::valarray<_Tp>'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0,
                 from retro.cpp:1:
/usr/include/c++/7/valarray:1186:1: note: candidate: template<class _Tp> std::_Expr<std::_BinClos<std::__less, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__less, _Tp>::result_type> std::operator<(const std::valarray<_Tp>&, const _Tp&)
 _DEFINE_BINARY_OPERATOR(<, __less)
 ^
/usr/include/c++/7/valarray:1186:1: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::valarray<_Tp>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0,
                 from retro.cpp:1:
/usr/include/c++/7/valarray:1186:1: note: candidate: template<class _Tp> std::_Expr<std::_BinClos<std::__less, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__less, _Tp>::result_type> std::operator<(const std::valarray<_Tp>&, const std::valarray<_Tp>&)
 _DEFINE_BINARY_OPERATOR(<, __less)
 ^
/usr/include/c++/7/valarray:1186:1: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::valarray<_Tp>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from retro.cpp:1:
/usr/include/c++/7/bits/valarray_after.h:416:5: note: candidate: template<class _Dom> std::_Expr<std::_BinClos<std::__less, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const std::valarray<typename _Dom::value_type>&, const std::_Expr<_Dom1, typename _Dom1::value_type>&)
     _DEFINE_EXPR_BINARY_OPERATOR(<, __less)
     ^
/usr/include/c++/7/bits/valarray_after.h:416:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from retro.cpp:1:
/usr/include/c++/7/bits/valarray_after.h:416:5: note: candidate: template<class _Dom> std::_Expr<std::_BinClos<std::__less, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::valarray<typename _Dom::value_type>&)
     _DEFINE_EXPR_BINARY_OPERATOR(<, __less)
     ^
/usr/include/c++/7/bits/valarray_after.h:416:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from retro.cpp:1:
/usr/include/c++/7/bits/valarray_after.h:416:5: note: candidate: template<class _Dom> std::_Expr<std::_BinClos<std::__less, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const typename _Dom::value_type&, const std::_Expr<_Dom1, typename _Dom1::value_type>&)
     _DEFINE_EXPR_BINARY_OPERATOR(<, __less)
     ^
/usr/include/c++/7/bits/valarray_after.h:416:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from retro.cpp:1:
/usr/include/c++/7/bits/valarray_after.h:416:5: note: candidate: template<class _Dom> std::_Expr<std::_BinClos<std::__less, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)
     _DEFINE_EXPR_BINARY_OPERATOR(<, __less)
     ^
/usr/include/c++/7/bits/valarray_after.h:416:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from retro.cpp:1:
/usr/include/c++/7/bits/valarray_after.h:416:5: note: candidate: template<class _Dom1, class _Dom2> std::_Expr<std::_BinClos<std::__less, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::_Expr<_Dom2, typename _Dom2::value_type>&)
     _DEFINE_EXPR_BINARY_OPERATOR(<, __less)
     ^
/usr/include/c++/7/bits/valarray_after.h:416:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/stack:61:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:89,
                 from retro.cpp:1:
/usr/include/c++/7/bits/stl_stack.h:311:5: note: candidate: template<class _Tp, class _Seq> bool std::operator<(const std::stack<_Tp, _Seq>&, const std::stack<_Tp, _Seq>&)
     operator<(const stack<_Tp, _Seq>& __x, const stack<_Tp, _Seq>& __y)
     ^~~~~~~~
/usr/include/c++/7/bits/stl_stack.h:311:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::stack<_Tp, _Seq>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/set:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:87,
                 from retro.cpp:1:
/usr/include/c++/7/bits/stl_multiset.h:913:5: note: candidate: template<class _Key, class _Compare, class _Alloc> bool std::operator<(const std::multiset<_Key, _Compare, _Alloc>&, const std::multiset<_Key, _Compare, _Alloc>&)
     operator<(const multiset<_Key, _Compare, _Alloc>& __x,
     ^~~~~~~~
/usr/include/c++/7/bits/stl_multiset.h:913:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::multiset<_Key, _Compare, _Alloc>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/set:61:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:87,
                 from retro.cpp:1:
/usr/include/c++/7/bits/stl_set.h:930:5: note: candidate: template<class _Key, class _Compare, class _Alloc> bool std::operator<(const std::set<_Key, _Compare, _Alloc>&, const std::set<_Key, _Compare, _Alloc>&)
     operator<(const set<_Key, _Compare, _Alloc>& __x,
     ^~~~~~~~
/usr/include/c++/7/bits/stl_set.h:930:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::set<_Key, _Compare, _Alloc>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/queue:64:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:86,
                 from retro.cpp:1:
/usr/include/c++/7/bits/stl_queue.h:336:5: note: candidate: template<class _Tp, class _Seq> bool std::operator<(const std::queue<_Tp, _Seq>&, const std::queue<_Tp, _Seq>&)
     operator<(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
     ^~~~~~~~
/usr/include/c++/7/bits/stl_queue.h:336:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::queue<_Tp, _Seq>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/vector:64:0,
                 from /usr/include/c++/7/queue:61,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:86,
                 from retro.cpp:1:
/usr/include/c++/7/bits/stl_vector.h:1613:5: note: candidate: template<class _Tp, class _Alloc> bool std::operator<(const std::vector<_Tp, _Alloc>&, const std::vector<_Tp, _Alloc>&)
     operator<(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
     ^~~~~~~~
/usr/include/c++/7/bits/stl_vector.h:1613:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::vector<_Tp, _Alloc>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/memory:81:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:82,
                 from retro.cpp:1:
/usr/include/c++/7/bits/shared_ptr.h:416:5: note: candidate: template<class _Tp> bool std::operator<(std::nullptr_t, const std::shared_ptr<_Tp>&)
     operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
     ^~~~~~~~
/usr/include/c++/7/bits/shared_ptr.h:416:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::shared_ptr<_Tp>'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/memory:81:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:82,
                 from retro.cpp:1:
/usr/include/c++/7/bits/shared_ptr.h:408:5: note: candidate: template<class _Tp> bool std::operator<(const std::shared_ptr<_Tp>&, std::nullptr_t)
     operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
     ^~~~~~~~
/usr/include/c++/7/bits/shared_ptr.h:408:5: note:   template argument deduction/substitution failed:
retro.cpp:76:29: note:   mismatched types 'const std::shared_ptr<_Tp>' and 'int'
         for (int i = 0; i < ans; i++)
                             ^~~
In file included from /usr/include/c++/7/memory:81:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:82,
                 from retro.cpp:1:
/usr/include/c++/7/bits/shared_ptr.h:398:5: note: candidate: template<class _Tp, class _Up> bool std::operator<(const std::shared_ptr<_Tp>&, const std::shared_ptr<_Up>&)
     operator<(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
     ^~~~~~~~
/usr/include/c++/7/bits/shared_ptr.h:398:5: note:   template argument de