Language: C++

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
typedef long long ll;
typedef pair<int, int> P;

const int INF = 1e9 + 5;

// input
int N, W;
vector<int> w, v;

vector<map<ll, ll>> m;


void input() {
    cin >> N >> W;
    w = v = vector<int>(N);
    rep(i, N) cin >> w[i] >> v[i];
}


int main() {
    input();
    m = vector<map<ll, ll>>(N + 1);
    rep(k, N + 1) rep(i, k + 1) rep(j, 4 * i) m[k][i * w[0] + j] = -INF;
    m[0][0] = 0;
    for (int i = 1; i <= N; i++) {
        rep(j, i + 1) rep(k, 4 * j) {
            int x = j * w[0] + k;
            if (W < x) continue;
            m[i][x] = m[i - 1][x];
            int y = x - w[i - 1];
            if (m[i - 1].count(y)) m[i][x] = max(m[i][x], m[i - 1][y] + v[i - 1]);
        }
    }
    int ans = 0;
    rep(i, N + 1) rep(j, 4 * i) ans = max(ans, m[N][i * w[0] + j]);
    cout << ans << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:38:42: error: no matching function for call to 'max(int&, std::map<long long int, long long int>::mapped_type&)'
   38 |     rep(i, N + 1) rep(j, 4 * i) ans = max(ans, m[N][i * w[0] + j]);
      |                                       ~~~^~~~~~~~~~~~~~~~~~~~~~~~~
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:38:42: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'std::map<long long int, long long int>::mapped_type' {aka 'long long int'})
   38 |     rep(i, N + 1) rep(j, 4 * i) ans = max(ans, m[N][i * w[0] + j]);
      |                                       ~~~^~~~~~~~~~~~~~~~~~~~~~~~~
/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:38:42: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   38 |     rep(i, N + 1) rep(j, 4 * i) ans = max(ans, m[N][i * w[0] + j]);
      |                                       ~~~^~~~~~~~~~~~~~~~~~~~~~~~~