Submission #546248

#	Time	Username	Problem	Language	Result	Execution time	Memory
546248		Ooops_sorry	Beads and wires (APIO14_beads)	C++14	100 / 100	230 ms	42060 KiB

beads

#include<bits/stdc++.h>

using namespace std;

#define int long long
#define pb push_back
#define ld double
#define ll __int128

mt19937 rnd(51);

const int N = 2e5 + 10, INF = 1e18;
vector<pair<int,int>> g[N];
int res[N][2][2];

void dfs(int v, int p) {
    bool was = 0;
    vector<vector<int>> dp(3, vector<int>(3, -INF));
    dp[0][0] = 0;
    for (auto [to, c] : g[v]) {
        if (to != p) {
            dfs(to, v);
            was = 1;
            vector<vector<int>> dpp(3, vector<int>(3, -INF));
            for (int j = 0; j < 3; j++) {
                for (int k = 0; k < 3; k++) {
                    if (dp[j][k] == -INF) continue;
                    dpp[j][k] = max({dpp[j][k], dp[j][k] + res[to][1][1] + c, dp[j][k] + res[to][1][0]});
                    if (j + 1 < 3) {
                        if (k != 1) dpp[j + 1][k] = max(dpp[j + 1][k], dp[j][k] + res[to][1][0] + c);
                    }
                    if (k == 0) {
                        if (j == 0) {
                            dpp[j][1] = max(dpp[j][1], dp[j][k] + res[to][0][0]);
                            dpp[j][1] = max(dpp[j][1], dp[j][k] + res[to][0][1] + c);
                        }
                        if (j + 1 < 3) {
                            dpp[j + 1][2] = max(dpp[j + 1][2], dp[j][k] + res[to][0][0] + c);
                        }
                    }
                }
            }
            swap(dp, dpp);
        }
    }
    if (!was) {
        res[v][0][0] = res[v][0][1] = res[v][1][1] = -INF;
        res[v][1][0] = 0;
    } else {
        res[v][1][1] = dp[1][0];
        res[v][1][0] = dp[0][0];
        res[v][0][0] = max({dp[0][1], dp[2][0], dp[2][1], dp[2][2]});
        res[v][0][1] = dp[1][2];
    }
}

signed main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
#endif // LOCAL
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    for (int i = 0; i < n - 1; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        a--, b--;
        g[a].pb({b, c});
        g[b].pb({a, c});
    }
    dfs(0, -1);
    cout << max(res[0][0][0], res[0][1][0]) << endl;
    return 0;
}

Compilation message (stderr)

beads.cpp: In function 'void dfs(long long int, long long int)':
beads.cpp:20:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   20 |     for (auto [to, c] : g[v]) {
      |               ^

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