Language: C++

#include<bits/stdc++.h>
#include<cctype>
using namespace std;
#define rep(i,n) for (int i=0;i<(n);i++)
#define all(v) (v).begin(),(v).end()
typedef long long int ll;
#define pi 3.1415926535897932384
#define E9 1000000000
#define eps 1e-4
#define pii pair<int,int>

int main(){
  int N, M; cin >> N >> M;
  vector<bool> dp(N,0);
  vector<int> ball(N,1);
  dp[0] = 1;

  int x, y;
  rep(i,M){
    cin >> x >> y;
    x--,y--;
    ball[x]--;
    ball[y]++;
    dp[y] |= dp[x];
    if (ball[x]==0) dp[x] = false;
  }

  int cnt = 0;
  rep(i,N) if (dp[i]) cnt++;
  cout << cnt << endl;


  // cout << fixed << setprecision(10);
  
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:24:11: error: no match for 'operator|=' (operand types are 'std::vector<bool>::reference' and 'std::vector<bool>::reference')
   24 |     dp[y] |= dp[x];
      |     ~~~~~~^~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:41,
                 from a.cc:1:
/usr/include/c++/14/cstddef:168:3: note: candidate: 'constexpr std::byte& std::operator|=(byte&, byte)'
  168 |   operator|=(byte& __l, byte __r) noexcept
      |   ^~~~~~~~
/usr/include/c++/14/cstddef:168:20: note:   no known conversion for argument 1 from 'std::vector<bool>::reference' to 'std::byte&'
  168 |   operator|=(byte& __l, byte __r) noexcept
      |              ~~~~~~^~~
In file included from /usr/include/c++/14/streambuf:43,
                 from /usr/include/c++/14/bits/streambuf_iterator.h:35,
                 from /usr/include/c++/14/iterator:66,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:54:
/usr/include/c++/14/bits/ios_base.h:104:3: note: candidate: 'constexpr const std::_Ios_Fmtflags& std::operator|=(_Ios_Fmtflags&, _Ios_Fmtflags)'
  104 |   operator|=(_Ios_Fmtflags& __a, _Ios_Fmtflags __b) _GLIBCXX_NOTHROW
      |   ^~~~~~~~
/usr/include/c++/14/bits/ios_base.h:104:29: note:   no known conversion for argument 1 from 'std::vector<bool>::reference' to 'std::_Ios_Fmtflags&'
  104 |   operator|=(_Ios_Fmtflags& __a, _Ios_Fmtflags __b) _GLIBCXX_NOTHROW
      |              ~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/ios_base.h:154:3: note: candidate: 'constexpr const std::_Ios_Openmode& std::operator|=(_Ios_Openmode&, _Ios_Openmode)'
  154 |   operator|=(_Ios_Openmode& __a, _Ios_Openmode __b) _GLIBCXX_NOTHROW
      |   ^~~~~~~~
/usr/include/c++/14/bits/ios_base.h:154:29: note:   no known conversion for argument 1 from 'std::vector<bool>::reference' to 'std::_Ios_Openmode&'
  154 |   operator|=(_Ios_Openmode& __a, _Ios_Openmode __b) _GLIBCXX_NOTHROW
      |              ~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/ios_base.h:201:3: note: candidate: 'constexpr const std::_Ios_Iostate& std::operator|=(_Ios_Iostate&, _Ios_Iostate)'
  201 |   operator|=(_Ios_Iostate& __a, _Ios_Iostate __b) _GLIBCXX_NOTHROW
      |   ^~~~~~~~
/usr/include/c++/14/bits/ios_base.h:201:28: note:   no known conversion for argument 1 from 'std::vector<bool>::reference' to 'std::_Ios_Iostate&'
  201 |   operator|=(_Ios_Iostate& __a, _Ios_Iostate __b) _GLIBCXX_NOTHROW
      |              ~~~~~~~~~~~~~~^~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:176:
/usr/include/c++/14/future:185:18: note: candidate: 'constexpr std::launch& std::operator|=(launch&, launch)'
  185 |   inline launch& operator|=(launch& __x, launch __y) noexcept
      |                  ^~~~~~~~
/usr/include/c++/14/future:185:37: note:   no known conversion for argument 1 from 'std::vector<bool>::reference' to 'std::launch&'
  185 |   inline launch& operator|=(launch& __x, launch __y) noexcept
      |                             ~~~~~~~~^~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:198:
/usr/include/c++/14/charconv:646:3: note: candidate: 'constexpr std::chars_format& std::operator|=(chars_format&, chars_format)'
  646 |   operator|=(chars_format& __lhs, chars_format __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/14/charconv:646:28: note:   no known conversion for argument 1 from 'std::vector<bool>::reference' to 'std::chars_format&'
  646 |   operator|=(chars_format& __lhs, chars_format __rhs) noexcept
      |              ~~~~~~~~~~~~~~^~~~~