Language: C++

#include<iostream>
#include<algorithm>
#include<string>
#include<functional>
#include<utility>
#include<ctime>
#include<cmath>
#include<vector>
#include<set>
#include<queue>
#include<deque>
#include<map>
#include<cstring>
#include<stack>
#include<cctype>
#include<cstdio>
#include<bitset>
#ifdef LOCAL
	#define enu(i,n) for(int i=0;i<n;i++)
	#define tri(x) x*(x+1)/2;
	#define sqrsum(x) x*(x+1)*(2*x+1)/6;
	#define sqrsum_range(a,b) sqrsum(b)-sqrsum(a-1);
#endif
#define FOR(i,a,b) for(int i=a,_b=b;i<_b;i++)
#define REP(i,a,b) FOR(i,a,b+1)
#define ll_max 9223372036854775807LL
#define ll_min -9223372036854775808LL
#define int_max 2147483647
#define int_min -2147483648
#define PI 3.141592653589793238462653383
#define eps 0.00000001
#define elif else if
using namespace std;
void fast()
{
	cin.tie(NULL);
	cout.tie(NULL);
	ios_base::sync_with_stdio(false);
	return ;
}
bool isprime(int x)
{
	if(x<2)
		return false;
	for(int i=2;i<=sqrt(x);i++)
		if(x%i==0)
			return false;
	return true;
}
int GCD(int a,int b)
{
	return (b?GCD(b,a%b):a);
}
struct Tm
{
	int h,m,s;
	bool add()
	{
		s++;
		if(s==60)
			m++,
			s=0;
		if(m==60)
			h++,
			m=0;
		return (h<100);
	}
	void print()
	{
		printf("%02d:%02d:%02d",h,m,s);
		return ;
	}
	void println()
	{
		print();
		puts("");
	}
};
#define MAX(i,j) *max_element(i,i+j)
#define MIN(i,j) *min_element(i,i+j)
bool G[210][210];
int N,CntCir;
short X[210];
int st[100100],end[100100],p;
void dfs(int x,int pre)
{
	X[x]++;
	for(int i=0;i<N;i++)
		if(G[x][i]&&i!=pre)
		{
			if(X[i]==1)
				CntCir++,
				st[p]=i,
				end[p++]=x;
			else	dfs(i,x);
		}
	X[x]++;
	return ;
}
int dist[210];
bool bfsck()
{
	for(int i=0;i<p;i++)
	{
		G[st[i]][end[i]]=G[end[i]][st[i]]=0;
		queue<int> Q;
		for(int j=0;j<N;j++)
			dist[j]=-1;
		Q.push(st[i]);
		dist[st[i]]=0;
		while(!Q.empty())
		{
			int x=Q.front();
			Q.pop();
			for(int j=0;j<N;j++)
				if(G[x][j]&&dist[j]==-1)
					dist[j]=dist[x]+1,
					Q.push(j);
		}
		if(dist[end[i]]%2==0)
			return false;
		G[st[i]][end[i]]=G[end[i]][st[i]]=1;
	}
	return true;
}
int main()
{
	cin>>N;
	for(int i=0;i<N;i++)
		for(int j=0;j<N;j++)
			scanf("%1d",&G[i][j]);
	dfs(0,0);
	if(bfsck())
		cout<<N-CntCir<<endl;
	else	puts("-1");
	return 0;
}

Compiler output:
a.cc: In function 'void dfs(int, int)':
a.cc:94:33: error: reference to 'end' is ambiguous
   94 |                                 end[p++]=x;
      |                                 ^~~
In file included from /usr/include/c++/14/string:53,
                 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/range_access.h:116:37: note: candidates are: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
  116 |   template<typename _Tp> const _Tp* end(const valarray<_Tp>&) noexcept;
      |                                     ^~~
/usr/include/c++/14/bits/range_access.h:115:31: note:                 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
  115 |   template<typename _Tp> _Tp* end(valarray<_Tp>&) noexcept;
      |                               ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
In file included from /usr/include/c++/14/bits/range_access.h:36:
/usr/include/c++/14/initializer_list:99:5: note:                 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
a.cc:84:16: note:                 'int end [100100]'
   84 | int st[100100],end[100100],p;
      |                ^~~
a.cc: In function 'bool bfsck()':
a.cc:105:26: error: reference to 'end' is ambiguous
  105 |                 G[st[i]][end[i]]=G[end[i]][st[i]]=0;
      |                          ^~~
/usr/include/c++/14/bits/range_access.h:116:37: note: candidates are: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
  116 |   template<typename _Tp> const _Tp* end(const valarray<_Tp>&) noexcept;
      |                                     ^~~
/usr/include/c++/14/bits/range_access.h:115:31: note:                 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
  115 |   template<typename _Tp> _Tp* end(valarray<_Tp>&) noexcept;
      |                               ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:                 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
a.cc:84:16: note:                 'int end [100100]'
   84 | int st[100100],end[100100],p;
      |                ^~~
a.cc:105:36: error: reference to 'end' is ambiguous
  105 |                 G[st[i]][end[i]]=G[end[i]][st[i]]=0;
      |                                    ^~~
/usr/include/c++/14/bits/range_access.h:116:37: note: candidates are: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
  116 |   template<typename _Tp> const _Tp* end(const valarray<_Tp>&) noexcept;
      |                                     ^~~
/usr/include/c++/14/bits/range_access.h:115:31: note:                 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
  115 |   template<typename _Tp> _Tp* end(valarray<_Tp>&) noexcept;
      |                               ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:                 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
a.cc:84:16: note:                 'int end [100100]'
   84 | int st[100100],end[100100],p;
      |                ^~~
a.cc:120:25: error: reference to 'end' is ambiguous
  120 |                 if(dist[end[i]]%2==0)
      |                         ^~~
/usr/include/c++/14/bits/range_access.h:116:37: note: candidates are: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
  116 |   template<typename _Tp> const _Tp* end(const valarray<_Tp>&) noexcept;
      |                                     ^~~
/usr/include/c++/14/bits/range_access.h:115:31: note:                 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
  115 |   template<typename _Tp> _Tp* end(valarray<_Tp>&) noexcept;
      |                               ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:                 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
a.cc:84:16: note:                 'int end [100100]'
   84 | int st[100100],end[100100],p;
      |                ^~~
a.cc:122:26: error: reference to 'end' is ambiguous
  122 |                 G[st[i]][end[i]]=G[end[i]][st[i]]=1;
      |                          ^~~
/usr/include/c++/14/bits/range_access.h:116:37: note: candidates are: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
  116 |   template<typename _Tp> const _Tp* end(const valarray<_Tp>&) noexcept;
      |                                     ^~~
/usr/include/c++/14/bits/range_access.h:115:31: note:                 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
  115 |   template<typename _Tp> _Tp* end(valarray<_Tp>&) noexcept;
      |                               ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:                 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
a.cc:84:16: note:                 'int end [100100]'
   84 | int st[100100],end[100100],p;
      |                ^~~
a.cc:122:36: error: reference to 'end' is ambiguous
  122 |                 G[st[i]][end[i]]=G[end[i]][st[i]]=1;
      |                                    ^~~
/usr/include/c++/14/bits/range_access.h:116:37: note: candidates are: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
  116 |   template<typename _Tp> const _Tp* end(const valarray<_Tp>&) noexcept;
      |                                     ^~~
/usr/include/c++/14/bits/range_access.h:115:31: note:                 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
  115 |   template<typename _Tp> _Tp* end(valarray<_Tp>&) noexcept;
      |                               ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:                 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:                 'template<class _Tp> constexpr const _Tp* s