Language: C++

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

using ll = long long;

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define ddrep(i, n) for (int i = n; i > 0; --i)
#define srep(i, s, t) for (int i = s; i < t; ++i)
#define ssrep(i, s, t) for (int i = s; i <= t; ++i)

#define rng(a) a.begin(), a.end()
#define rrng(a) a.rbegin(), a.rend()
#define pb push_back
#define eb emplace_back
#define fi first
#define se second

#define chmax(x, y) (x = max(x, y))
#define chmin(x, y) (x = min(x, y))

using pi = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vs = vector<string>;
using vvs = vector<vs>;
using ld = long double;

template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
    os << "(" << p.first << "," << p.second << ")";
    return os;
}

template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
    os << "{";
    rep(i, (int)v.size()) {
        if (i)
            os << ",";
        os << v[i];
    }
    os << "}";
    return os;
}

template <typename T, size_t S> void printArray(const T (&array)[S]) {
    for (auto val : array)
        std::cout << val << ", ";
    std::cout << "\n";
}

const int mod = 1e9 + 7;
const int inf = 1e9 + 5;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << std::setprecision(10);

    int n, m; std::cin >> n >> m;
    vvi to(n, vi(n, inf)), cost;
    rep(i, n) to[i][i] = 0;
    rep(i, m) {
        int a, b, c; std::cin >> a >> b >> c;
        --a, --b;
        to[a][b] = to[b][a] = c;
    }
    cost = to;
    rep(k, n) rep(i, n) rep(j, n) chmin(cost[i][j], cost[i][k] + cost[k][j]);
    set<pi> walked;
    rep(i, n) rep(j, n) {
        int s = i, g = j, cur = i;
        while (cur != g) {
            rep(k, n) {
                if (k == cur || to[cur][k]+cost[k][g] != cost[cur][g])
                    continue;
                walked.insert(cur, k);
                cur = k;
                break;
            }
        }
    }
    std::cout << m-(int)walked.size()/2 << "\n";
}


Compiler output:
In file included from /usr/include/c++/14/set:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:158,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_set.h: In instantiation of 'void std::set<_Key, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = int; _Key = std::pair<int, int>; _Compare = std::less<std::pair<int, int> >; _Alloc = std::allocator<std::pair<int, int> >]':
a.cc:81:30:   required from here
   81 |                 walked.insert(cur, k);
      |                 ~~~~~~~~~~~~~^~~~~~~~
/usr/include/c++/14/bits/stl_set.h:569:38: error: no matching function for call to 'std::_Rb_tree<std::pair<int, int>, std::pair<int, int>, std::_Identity<std::pair<int, int> >, std::less<std::pair<int, int> >, std::allocator<std::pair<int, int> > >::_M_insert_range_unique(int&, int&)'
  569 |         { _M_t._M_insert_range_unique(__first, __last); }
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/map:62,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:152:
/usr/include/c++/14/bits/stl_tree.h:1096:9: note: candidate: 'template<class _InputIterator> std::__enable_if_t<((bool)std::is_same<_Val, typename std::iterator_traits<_InputIterator>::value_type>::value)> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_range_unique(_InputIterator, _InputIterator) [with _Key = std::pair<int, int>; _Val = std::pair<int, int>; _KeyOfValue = std::_Identity<std::pair<int, int> >; _Compare = std::less<std::pair<int, int> >; _Alloc = std::allocator<std::pair<int, int> >]'
 1096 |         _M_insert_range_unique(_InputIterator __first, _InputIterator __last)
      |         ^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_tree.h:1096:9: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/stl_tree.h: In substitution of 'template<class _InputIterator> std::__enable_if_t<((bool)std::is_same<std::pair<int, int>, typename std::iterator_traits< <template-parameter-1-1> >::value_type>::value), void> std::_Rb_tree<std::pair<int, int>, std::pair<int, int>, std::_Identity<std::pair<int, int> >, std::less<std::pair<int, int> >, std::allocator<std::pair<int, int> > >::_M_insert_range_unique(_InputIterator, _InputIterator) [with _InputIterator = int]':
/usr/include/c++/14/bits/stl_set.h:569:31:   required from 'void std::set<_Key, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = int; _Key = std::pair<int, int>; _Compare = std::less<std::pair<int, int> >; _Alloc = std::allocator<std::pair<int, int> >]'
  569 |         { _M_t._M_insert_range_unique(__first, __last); }
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
a.cc:81:30:   required from here
   81 |                 walked.insert(cur, k);
      |                 ~~~~~~~~~~~~~^~~~~~~~
/usr/include/c++/14/bits/stl_tree.h:1095:58: error: no type named 'value_type' in 'struct std::iterator_traits<int>'
 1095 |         __enable_if_t<__same_value_type<_InputIterator>::value>
      |                                                          ^~~~~
/usr/include/c++/14/bits/stl_set.h: In instantiation of 'void std::set<_Key, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = int; _Key = std::pair<int, int>; _Compare = std::less<std::pair<int, int> >; _Alloc = std::allocator<std::pair<int, int> >]':
a.cc:81:30:   required from here
   81 |                 walked.insert(cur, k);
      |                 ~~~~~~~~~~~~~^~~~~~~~
/usr/include/c++/14/bits/stl_tree.h:1105:9: note: candidate: 'template<class _InputIterator> std::__enable_if_t<((bool)(! std::is_same<_Val, typename std::iterator_traits<_InputIterator>::value_type>::value))> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_range_unique(_InputIterator, _InputIterator) [with _Key = std::pair<int, int>; _Val = std::pair<int, int>; _KeyOfValue = std::_Identity<std::pair<int, int> >; _Compare = std::less<std::pair<int, int> >; _Alloc = std::allocator<std::pair<int, int> >]'
 1105 |         _M_insert_range_unique(_InputIterator __first, _InputIterator __last)
      |         ^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_tree.h:1105:9: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/stl_tree.h: In substitution of 'template<class _InputIterator> std::__enable_if_t<((bool)(! std::is_same<std::pair<int, int>, typename std::iterator_traits< <template-parameter-1-1> >::value_type>::value)), void> std::_Rb_tree<std::pair<int, int>, std::pair<int, int>, std::_Identity<std::pair<int, int> >, std::less<std::pair<int, int> >, std::allocator<std::pair<int, int> > >::_M_insert_range_unique(_InputIterator, _InputIterator) [with _InputIterator = int]':
/usr/include/c++/14/bits/stl_set.h:569:31:   required from 'void std::set<_Key, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = int; _Key = std::pair<int, int>; _Compare = std::less<std::pair<int, int> >; _Alloc = std::allocator<std::pair<int, int> >]'
  569 |         { _M_t._M_insert_range_unique(__first, __last); }
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
a.cc:81:30:   required from here
   81 |                 walked.insert(cur, k);
      |                 ~~~~~~~~~~~~~^~~~~~~~
/usr/include/c++/14/bits/stl_tree.h:1104:59: error: no type named 'value_type' in 'struct std::iterator_traits<int>'
 1104 |         __enable_if_t<!__same_value_type<_InputIterator>::value>
      |                                                           ^~~~~