Submission #494902

#	Time	Username	Problem	Language	Result	Execution time	Memory
494902		Stickfish	Beads and wires (APIO14_beads)	C++17	57 / 100	1018 ms	17864 KiB

beads

#include <iostream>
#include <vector>
using namespace std;

const int MAXN = 2e5 + 123;
const int INF = 1.77013e9;
vector<pair<int, int>> edg[MAXN];
int dp[MAXN][2];

void update(int v, int rt) {
    dp[v][0] = dp[v][1] = 0;
    int rtw = -INF;
    for (auto [u, w] : edg[v]) {
        if (u == rt) {
            rtw = w;
            continue;
        }
        dp[v][0] += max(dp[u][0], dp[u][1]);
    }
    dp[v][1] = dp[v][0];
    if (rtw != -INF) {
        for (auto [u, w] : edg[v]) {
            if (u == rt)
                continue;
            dp[v][1] = max(dp[v][1], dp[v][0] + rtw + w + min(0, dp[u][0] - dp[u][1]));
        }
    }
}

void get_ans(int v, int rt) {
    for (auto [u, w] : edg[v]) {
        if (u == rt) {
            continue;
        }
        get_ans(u, v);
    }
    update(v, rt);
}

int dfs(int v, int rt) {
    int ans = dp[v][0];
    for (auto [u, w] : edg[v]) {
        if (u == rt)
            continue;
        update(v, u);
        update(u, -1);
        ans = max(ans, dfs(u, v));
        update(u, v);
        update(v, -1);
    }
    return ans;
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n;
    cin >> n;
    for (int i = 0; i < n - 1; ++i) {
        int u, v, d;
        cin >> u >> v >> d;
        --u, --v;
        edg[u].push_back({v, d});
        edg[v].push_back({u, d});
    }
    get_ans(0, -1);
    int ans = dfs(0, -1);
    cout << ans << endl;
}

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