Language: C++

#include<bits/stdc++.h>
#define rep(i,n) for (ll i = 0; i < (ll)(n); i++)
using namespace std;
using ll = long long;
using vl= vector<ll>;

int main(){
  ll n, m, k;
  cin >> n >> m >> k;
  vl a(n), b(m);
  rep(i,n) cin >> a[i];
  rep(i,m) cin >> b[i];
  
  //ーーーー累積和ーーーー//
  
  vl A(n), B(m);
  A[0] = a[0], B[0] = b[0];
  ll ans = 0;
  rep(i,n-1) A[i+1] = A[i] + a[i+1];
  rep(i,m-1) B[i+1] = B[i] + b[i+1];
  
  rep(i,m) if (B[i] <= k) ans = max(ans,i+1);
  
  //ーーーー二分探索ーーーー//
  //kからaのi番目までの累積和A[i]を引くことで残りの時間数keyが分かる。
  //keyがbの累積和Bではどこに当てはまるのかを二分探索で求める。
  //読んだ本の数は(i+1)と、二分探索で求めた(l+1)の和で与えられる。
  //これと、Bのみ貪欲に読んでいったときの本の数(ans)とで、大きい方を答にする。
  
  rep(i,n) {
    ll key = k - A[i];
    ll l = -1, r = m;
    if (key < 0) continue;
    if (key < A[0]) {
      ans = max(ans,i+1);
      continue;
    }
    
    ll it = lower_bound(B, B+m, key) - B;
    ans = max(i+1+it,ans);
  }
  cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:39:29: error: no match for 'operator+' (operand types are 'vl' {aka 'std::vector<long long int>'} and 'll' {aka 'long long int'})
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                            ~^~
      |                            | |
      |                            | ll {aka long long int}
      |                            vl {aka std::vector<long long int>}
In file included from /usr/include/c++/14/bits/stl_algobase.h:67,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:627:5: note: candidate: 'template<class _Iterator> constexpr std::reverse_iterator<_Iterator> std::operator+(typename reverse_iterator<_Iterator>::difference_type, const reverse_iterator<_Iterator>&)'
  627 |     operator+(typename reverse_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:627:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'll' {aka 'long long int'}
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note: candidate: 'template<class _Iterator> constexpr std::move_iterator<_IteratorL> std::operator+(typename move_iterator<_IteratorL>::difference_type, const move_iterator<_IteratorL>&)'
 1798 |     operator+(typename move_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'll' {aka 'long long int'}
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
In file included from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/basic_string.h:3598:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3598 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3598:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'vl' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3616:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3616 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3616:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   mismatched types 'const _CharT*' and 'std::vector<long long int>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3635:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3635 |     operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3635:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'll' {aka 'long long int'}
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3652:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3652 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3652:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'vl' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3670:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 3670 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3670:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'vl' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3682:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3682 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3682:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'vl' {aka 'std::vector<long long int>'} is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3689:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3689 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3689:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'vl' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3696:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3696 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3696:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'vl' {aka 'std::vector<long long int>'} is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3719:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3719 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3719:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   mismatched types 'const _CharT*' and 'std::vector<long long int>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3726:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3726 |     operator+(_CharT __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3726:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'll' {aka 'long long int'}
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3733:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const _CharT*)'
 3733 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3733:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'vl' {aka 'std::vector<long long int>'} is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   39 |     ll it = lower_bound(B, B+m, key) - B;
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3740:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, _CharT)'
 3740 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3740:5: note:   template argument deduction/substitution failed:
a.cc:39:30: note:   'vl' {aka 'std::vector<long long int>'} is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'