Submission #541699

#	Time	Username	Problem	Language	Result	Execution time	Memory
541699		Aldas25	Beads and wires (APIO14_beads)	C++14	0 / 100	4 ms	5036 KiB

beads

#include <bits/stdc++.h>

using namespace std;

#define FAST_IO ios_base::sync_with_stdio(0); cin.tie(nullptr)
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define REP(n) FOR(O, 1, (n))
#define f first
#define s second
#define pb push_back
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
typedef long double ld;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int MAXN = 200100;
const ll INF = 1e16;

int n;
vector<pair<int, ll>> adj[MAXN];
ll dp[MAXN][2][2], mx[MAXN];

void dfs (int v, int p, ll pw = -1) {
    ll mx1 = -INF, mx2 = -INF;

    for (auto e : adj[v]) {
        int u = e.f;
        ll w = e.s;
        if (u == p) continue;
        dfs (u, v, w);

        dp[v][0][0] += mx[u];
        dp[v][1][0] += mx[u];
        dp[v][1][1] += mx[u];

        ll cr = w;
        if (mx[u] == dp[u][1][1])
            cr = cr - mx[u] + max(dp[u][1][0], dp[u][0][0]);

        if (cr > mx2) swap(cr, mx2);
        if (mx2 > mx1) swap(mx2, mx1);
    }

    if (p != -1 && mx1 != -INF) {
        dp[v][1][1] += pw + mx1;
    }
    if (mx2 != -INF) {
        dp[v][1][0] += mx2 + mx1;
    }

    FOR(a, 0, 1) FOR(b, 0, 1) mx[v] = max(mx[v], dp[v][a][b]);
}

int main()
{
    FAST_IO;

    cin >> n;
    REP(n-1) {
        int u, v;
        ll w;
        cin >> u >> v >> w;
        adj[u].pb({v, w});
        adj[v].pb({u, w});
    }

    dfs(1, -1);

    cout << mx[1] << "\n";

    return 0;
}

/*


5
1 2 10
1 3 40
1 4 15
1 5 20

10
4 10 2
1 2 21
1 3 13
6 7 1
7 9 5
2 4 3
2 5 8
1 6 55
6 8 34
*/

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