Submission #1248035

#	Time	Username	Problem	Language	Result	Execution time	Memory
1248035		uakkes	Museum (CEOI17_museum)	C++20	100 / 100	258 ms	140684 KiB

museum

//
// All truth are easy to understand once they are discovered.
// The point is to discover them
//
#include <bits/stdc++.h>
using namespace std;

const int N = 1e4 + 1;
vector<pair<int, int>> g[N];
vector<int> dp[N][2];
int sz[N], ndp[N + N][2];
// 0 - went backwards
// 1 - did not went backwards

void dfs(int v, int p) {
    sz[v] = 1;
    for (auto [u, c] : g[v]) {
        if (u == p) continue;
        dfs(u, v);
        sz[v] += sz[u];
    }

    dp[v][0].resize(sz[v] + 1, 1e9);
    dp[v][1].resize(sz[v] + 1, 1e9);
    dp[v][0][1] = 0;
    dp[v][1][1] = 0;

    for (auto [u, c] : g[v]) {
        if (u == p) continue;
        for (int i = 0; i <= sz[v] + sz[u]; i++) {
            ndp[i][0] = ndp[i][1] = 1e9;
        }
        for (int i = 1; i <= sz[v]; i++) {
            if (dp[v][0][i] == 1e9) break;
            for (int j = 1; j <= sz[u]; j++) {
                ndp[i + j][0] = min(ndp[i + j][0], dp[v][0][i] + dp[u][0][j] + c * 2);
                ndp[i + j][1] = min(ndp[i + j][1], dp[v][1][i] + dp[u][0][j] + c * 2);
                ndp[i + j][1] = min(ndp[i + j][1], dp[v][0][i] + dp[u][1][j] + c);
            }
        }
        for (int i = 0; i <= sz[v]; i++) {
            dp[v][0][i] = min(dp[v][0][i], ndp[i][0]);
            dp[v][1][i] = min(dp[v][1][i], ndp[i][1]);
        }
    }
}

void solve(){
    int n, k, x;
    cin >> n >> k >> x;

    for (int i = 1, c, u, v; i < n; i++) {
        cin >> u >> v >> c;
        g[u].emplace_back(v, c);
        g[v].emplace_back(u, c);
    }

    dfs(x, -1);
    cout << dp[x][1][k];
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int tt = 1;
    // cin >> tt;

    while (tt--) {
        solve();
        cout << '\n';
    }

    return 0;
}

• Subtask 1: 20 / 20
• Subtask 2: 25 / 25
• Subtask 3: 35 / 35
• Subtask 4: 20 / 20