Submission #924992

#	Time	Username	Problem	Language	Result	Execution time	Memory
924992		thinknoexit	Beads and wires (APIO14_beads)	C++17	100 / 100	104 ms	29020 KiB

beads

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 200200;
const ll INF = 5e17;
vector<pair<int, int>> adj[N];
ll dp[4][N];
void dfs(int v, int p = -1) {
    ll mx0 = 0;
    pair<ll, int> mxr[2] = { {-INF,0}, {-INF,0} };
    pair<ll, int> mxb[2] = { {-INF,0}, {-INF,0} };
    for (auto& [x, w] : adj[v]) {
        if (x == p) continue;
        dfs(x, v);
        ll val = max(dp[1][x], dp[2][x] + w);
        dp[0][v] += val;
        dp[1][v] += val;
        dp[2][v] += val;
        dp[3][v] += val;
        mx0 = max(mx0, max(dp[0][x], dp[3][x] + w) - val);
        mxr[1] = max(mxr[1], { dp[1][x] + w - val, x });
        mxb[1] = max(mxb[1], { dp[0][x] + w - val, x });
        if (mxr[0] < mxr[1]) swap(mxr[0], mxr[1]);
        if (mxb[0] < mxb[1]) swap(mxb[0], mxb[1]);
    }
    ll mx1;
    if (mxr[0].second != mxb[0].second) mx1 = mxr[0].first + mxb[0].first;
    else mx1 = max(mxr[0].first + mxb[1].first, mxr[1].first + mxb[0].first);
    dp[0][v] += max(mx0, mx1);
    dp[2][v] += mxr[0].first;
    dp[3][v] += mxb[0].first;
}
int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n;
    cin >> n;
    for (int i = 1;i < n;i++) {
        int u, v, w;
        cin >> u >> v >> w;
        adj[u].push_back({ v, w });
        adj[v].push_back({ u, w });
    }
    dfs(1);
    cout << max(dp[0][1], dp[1][1]);
    return 0;
}

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