Submission #404142

#	Time	Username	Problem	Language	Result	Execution time	Memory
404142		opukittpceno_hhr	Beads and wires (APIO14_beads)	C++17	100 / 100	439 ms	46556 KiB

beads

#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <fstream>
#include <cassert>
#include <cstring>
#include <unordered_set>
#include <unordered_map>
#include <numeric>
#include <ctime>
#include <bitset>
#include <complex>
#include <chrono>
#include <random>
#include <functional>

using namespace std;

#define int long long

const int INF = 1e18 + 239;
const int N = 2e5 + 7;

int rP[N];
int to[N];
int dp[N][2];
int udp[N][2];

vector<pair<int, int>> g[N];

void dfs(int cur, int p) {
    rP[cur] = p;
    int S = 0;
    int mx = -INF;
    for (auto [t, w] : g[cur]) {
        if (t != p) {
            to[t] = w;
            dfs(t, cur);
            S += max(dp[t][0], dp[t][1]);
            mx = max(mx, dp[t][0] + to[t] - max(dp[t][0], dp[t][1]));
        }
    }
    dp[cur][1] = S + mx + to[cur];
    dp[cur][0] = S;
}

void dfs2(int cur, int p) {
    int S = 0;
    multiset<int> smx = {-INF};
    if (p != -1) {
        S += max(udp[cur][0], udp[cur][1]);
        smx.insert(udp[cur][0] + to[cur] - max(udp[cur][0], udp[cur][1]));
    }
    for (auto [t, w] : g[cur]) {
        if (t != p) {
            S += max(dp[t][0], dp[t][1]);
            smx.insert(dp[t][0] + to[t] - max(dp[t][0], dp[t][1]));
        }
    }
    for (auto [t, w] : g[cur]) {
        if (t != p) {
            S -= max(dp[t][0], dp[t][1]);
            smx.erase(smx.find(dp[t][0] + to[t] - max(dp[t][0], dp[t][1])));
            udp[t][0] = S;
            udp[t][1] = S + *smx.rbegin() + to[t];
            S += max(dp[t][0], dp[t][1]);
            smx.insert(dp[t][0] + to[t] - max(dp[t][0], dp[t][1]));
        }
    }
    for (auto [t, w] : g[cur]) {
        if (t != p) {
            dfs2(t, cur);
        }
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;
    for (int i = 0; i + 1 < n; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        u--;
        v--;
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    dfs(0, -1);
    dfs2(0, -1);
    int ans = 0;
    for (int i = 0; i < n; i++) {
        int c = 0;
        for (auto [j, w] : g[i]) {
            if (j == rP[i]) {
                c += max(udp[i][0], udp[i][1]);
            } else {
                c += max(dp[j][0], dp[j][1]);
            }
        }
        ans = max(ans, c);
    }
    cout << ans << '\n';
}

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