Language: C++

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

#define rep(i, n) for(int i = 0; i < (n); i++)
using LL = long long;
using ULL = unsigned long long;


void solve() {
	unsigned n; cin >> n;
	vector<vector<pair<unsigned, unsigned>>> e(n);
	rep(i, n - 1) {
		int a, b; cin >> a >> b;
		a--; b--;
		e[a].push_back({ b, i });
		e[b].push_back({ a, i });
	}
	unsigned m = 0; rep(i, n) { m = max(m, e[i].size()); }
	vector<pair<unsigned, unsigned>> ncol(n);
	rep(i, n) ncol[i] = { 0, -1 };
	vector<unsigned> ecol(n - 1);
	stack<unsigned> st; st.push(0);
	while (!st.empty()) {
		unsigned p = st.top(); st.pop();
		unsigned skipc = ncol[p].first;
		unsigned skipn = ncol[p].second;
		unsigned colori = 1;
		rep(i, e[p].size()) {
			auto pe = e[p][i];
			if (skipn == pe.first) continue;
			if (colori == skipc) colori++;
			ncol[pe.first].first = colori;
			ncol[pe.first].second = p;
			ecol[pe.second] = colori;
			st.push(pe.first);
			colori++;
		}
	}

	cout << m << endl;
	rep(i, n - 1) cout << ecol[i] << endl;
}

int main() {

	solve();

	return 0;
}


Compiler output:
a.cc: In function 'void solve()':
a.cc:19:44: error: no matching function for call to 'max(unsigned int&, std::vector<std::pair<unsigned int, unsigned int> >::size_type)'
   19 |         unsigned m = 0; rep(i, n) { m = max(m, e[i].size()); }
      |                                         ~~~^~~~~~~~~~~~~~~~
In file included 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_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:19:44: note:   deduced conflicting types for parameter 'const _Tp' ('unsigned int' and 'std::vector<std::pair<unsigned int, unsigned int> >::size_type' {aka 'long unsigned int'})
   19 |         unsigned m = 0; rep(i, n) { m = max(m, e[i].size()); }
      |                                         ~~~^~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:19:44: note:   mismatched types 'std::initializer_list<_Tp>' and 'unsigned int'
   19 |         unsigned m = 0; rep(i, n) { m = max(m, e[i].size()); }
      |                                         ~~~^~~~~~~~~~~~~~~~