Language: C++

#include<bits/stdc++.h>
using namespace std;

#ifdef LOCAL
#include "debug_utils.h"
#else
#define print(...) ;
#define printn(...) ;
#endif

#define rep(i, a, b) for(auto i = (a); i < (b); i++)
#define rrep(i, a, b) for(auto i = (a); i > (b); i--)
#define all(v) (v).begin(), (v).end()
#define pb push_back

typedef unsigned long long ull;
typedef long long ll;
 
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
 
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<pdd> vpdd;
typedef vector<long long> vll;

const int MAXN = 1e5 + 10;

int n, m, t;
int x[MAXN], y[MAXN];
// vi points[MAXN];
int points[MAXN] ={};
unordered_set<int> pos[MAXN];
vi idxs[MAXN];
int tot = 0;

void cal1() {
	rrep(i, m - 1, -1) {
		if(pos[x[i]].size() == 0 && pos[y[i]].size() == 0) {
			points[tot]++;
			points[tot]++;
			pos[x[i]].insert(tot);
			pos[y[i]].insert(tot);
			idxs[tot].pb(i);
			tot++;
		}
		else {
			for(auto p : pos[x[i]]) {
				if(pos[y[i]].count(p)) continue;
				points[p]++;
				pos[y[i]].insert(p);
				idxs[p].pb(i);
			}
			for(auto p : pos[y[i]]) {
				if(pos[x[i]].count(p)) continue;
				points[p]++;
				pos[x[i]].insert(p);
				idxs[p].pb(i);
			}
		}
		if(pos[x[i]] == n || pos[y[i]] == n)
			break;
	}

	while(--tot >= 0) {
		if(points[tot] == n) break;
	}
	if(tot < 0) {
		cout << -1 << endl;
		return;
	}
	print(tot, points[tot], idxs[tot]);
	string res(m, '.');
	unordered_set<int> tmp;
	rep(i, 0, idxs[tot].size()) {
		auto idx = idxs[tot][i];
		if(tmp.count(x[idx]) != 0 && tmp.count(y[idx]) == 0)
			res[idx] = '^';
		if(tmp.count(x[idx]) == 0 && tmp.count(y[idx]) != 0)
			res[idx] = 'v';
		tmp.insert(x[idx]);
		tmp.insert(y[idx]);
		if(i + 1 < idxs[tot].size()) {
			rrep(j, idxs[tot][i] - 1, idxs[tot][i + 1] - 1) {
				if(tmp.count(x[j]) != 0 && tmp.count(y[j]) == 0)
					res[j] = '^';
				if(tmp.count(x[j]) == 0 && tmp.count(y[j]) != 0)
					res[j] = 'v';
			}
		}
	}
	for(auto & c : res)
		if(c == '.')
			c = '^';
	cout << res << endl;
}


int main(int argc, char * argv[]) {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    // if(argc > 1 && !strcmp(argv[1], debug.debug)) debug.on = true;

    cin >> n >> m >> t;
    rep(i, 0, m) cin >> x[i] >> y[i];

    if(t == 1) cal1();

    return 0;
}
















Compiler output:
a.cc: In function 'void cal1()':
a.cc:65:30: error: no match for 'operator==' (operand types are 'std::unordered_set<int>' and 'int')
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                    ~~~~~~~~~ ^~ ~
      |                            |    |
      |                            |    int
      |                            std::unordered_set<int>
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1103:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1103 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1103:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/regex.h:1199:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1199 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/regex.h:1274:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1274 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/regex.h:1366:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1366 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/regex.h:1441:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1441 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/regex.h:1534:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1534 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/regex.h:1613:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1613 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/regex.h:2186:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2186 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1033:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1033 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1033:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::pair<_T1, _T2>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:441:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  441 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:441:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/stl_iterator.h:486:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  486 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1667 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::move_iterator<_IteratorL>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1737 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::move_iterator<_IteratorL>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
In file included from /usr/include/c++/14/bits/char_traits.h:42,
                 from /usr/include/c++/14/string:42,
                 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/postypes.h:192:5: note: candidate: 'template<class _StateT> bool std::operator==(const fpos<_StateT>&, const fpos<_StateT>&)'
  192 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:192:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::fpos<_StateT>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
In file included from /usr/include/c++/14/string:43:
/usr/include/c++/14/bits/allocator.h:235:5: note: candidate: 'template<class _T1, class _T2> bool std::operator==(const allocator<_CharT>&, const allocator<_T2>&)'
  235 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:235:5: note:   template argument deduction/substitution failed:
a.cc:65:33: note:   'std::unordered_set<int>' is not derived from 'const std::allocator<_CharT>'
   65 |                 if(pos[x[i]] == n || pos[y[i]] == n)
      |                                 ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:629:5: note: candidate: 'template<class _CharT, class _Traits>