Submission #908136

#	Time	Username	Problem	Language	Result	Execution time	Memory
908136		duckindog	Beads and wires (APIO14_beads)	C++14	28 / 100	1018 ms	8792 KiB

beads

// from duckindog wth depression
#include<bits/stdc++.h>

using namespace std;

#define int long long

const int N = 2e5 + 10;
int n;
vector<pair<int, int>> ad[N];
int f[2][N];

void dfs(int u, int pre = 0) {

  int all = -1e15, none = -1e15;
  for (auto duck : ad[u]) {
    int v, w; tie(v, w) = duck;
    if (v == pre) continue;
    if (all == -1e15) all = 0;
    dfs(v, u);

    int best = max(f[1][v] + w, f[0][v]);
    all += best;
    none = max(none, f[0][v] + w - best);

  }
  f[0][u] = max(0ll, all);
  f[1][u] = all + none;

}

int32_t main() {
  cin.tie(0)->sync_with_stdio(0);

  if (fopen("duck.inp", "r")) {
    freopen("duck.inp", "r", stdin);
    freopen("duck.out", "w", stdout);
  }
  cin >> n;
  for (int i = 1; i < n; ++i) {
    int u, v, w; cin >> u >> v >> w;
    ad[u].push_back({v, w});
    ad[v].push_back({u, w});
  }

  int answer = 0;
  for (int i = 1; i <= n; ++i) {
    dfs(i);
    answer = max(answer, *max_element(f[0] + 1, f[0] + n + 1));
  }
  cout << answer;

}

Compilation message (stderr)

beads.cpp: In function 'int32_t main()':
beads.cpp:36:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |     freopen("duck.inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
beads.cpp:37:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |     freopen("duck.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43