Submission #1138355

#	Time	Username	Problem	Language	Result	Execution time	Memory
1138355		Pekiban	Beads and wires (APIO14_beads)	C++20	100 / 100	161 ms	34384 KiB

beads

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
#define pb push_back

const int N = 2e5 + 5;
const ll inf = 1e12;
ll dp[N][2][2];
vector<array<int, 2>> g[N];
void dfs(int s, int e = -1) {
    dp[s][0][0] = dp[s][1][0] = dp[s][1][1] = 0, dp[s][0][1] = -inf;
    for (auto [u, w] : g[s]) {
        if (u == e) continue;
        dfs(u, s);
        dp[s][0][0] += max(dp[u][0][0], dp[u][1][0] + w);
    }
    ll bs = -inf, bs2 = -inf;
    for (auto [u, w] : g[s]) {
        if (u == e) continue;
        bs = max(bs, dp[u][0][0] + w - max(dp[u][0][0], dp[u][1][0] + w));
        dp[s][1][0] += max(dp[u][0][0], dp[u][1][0] + w);
    }
    dp[s][1][0] += bs;
    bs = bs2 = -inf;
    vector<array<ll, 2>> V1 = {{-inf, 0}, {-inf, 0}}, V2 = {{-inf, 0}, {-inf, 0}};
    ll S = 0;
    for (auto [u, w] : g[s]) {
        if (u == e) continue;
        V1.pb({dp[u][0][0] + w - max(dp[u][0][0], dp[u][1][0] + w), u});
        V2.pb({dp[u][0][1] + w - max(dp[u][0][0], dp[u][1][0] + w), u});
        S += max(dp[u][0][0], dp[u][1][0] + w);
        bs = max(bs, max(dp[u][1][1] + w, dp[u][0][1]) - max(dp[u][0][0], dp[u][1][0] + w));
    }
    sort(V1.begin(), V1.end());
    sort(V2.begin(), V2.end());
    int sz = V1.size();
    // if (s == 1) {
    //     for (auto [a, b] : V1)  cout << a << ' ' << b << "||";
    //     cout << '\n';
    //     for (auto [a, b] : V2)  cout << a << ' ' << b << "||";
    //     cout << '\n';
    //     cout << S << ' ' << bs << '\n';
    // }
    dp[s][0][1] = S + max({bs, V1[sz-1][0] + V1[sz-2][0], (V1[sz-1][1] == V2[sz-1][1] ? max(V1[sz-1][0] + V2[sz-2][0], V1[sz-2][0] + V2[sz-1][0]) : V1[sz-1][0] + V2[sz-1][0])});
    bs = -inf;
    for (auto [u, w] : g[s]) {
        if (u == e) continue;
        bs = max(bs, dp[u][0][1] + w - max(dp[u][0][0], dp[u][1][0] + w));
        dp[s][1][1] += max(dp[u][0][0], dp[u][1][0] + w);
    }
    dp[s][1][1] += bs;
}
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    for (int i = 1; i < n; ++i) {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].pb({v, w}); 
        g[v].pb({u, w});
    }
    dfs(1);
    cout << max(dp[1][0][0], dp[1][0][1]) << '\n';
}

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