Submission #1220514

#	Time	Username	Problem	Language	Result	Execution time	Memory
1220514		LucaIlie	Mousetrap (CEOI17_mousetrap)	C++20	25 / 100	600 ms	64172 KiB

mousetrap

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 1e6;
const int MAX_N2 = 1e3;
const int INF = 1e9;
bool onPathTM[MAX_N + 1];
int parent[MAX_N + 1];
int dpArb[MAX_N + 1];
int dp[MAX_N2 + 1][MAX_N2 + 1];
vector<int> adj[MAX_N + 1];

void dfs(int u, int p) {
    parent[u] = p;
    for (int v: adj[u]) {
        if (v == p)
            continue;
        dfs(v, u);
    }
}

void calcDp(int u, int p) {
    int max1 = 0, max2 = 0;
    int sons = 0;
    for (int v: adj[u]) {
        if (v == p)
            continue;
        calcDp(v, u);

        if (!onPathTM[v]) {
            if (dpArb[v] > max1) {
                max2 = max1;
                max1 = dpArb[v];
            } else if (dpArb[v] > max2) 
                max2 = dpArb[v];
            sons++;
        }
    }

    dpArb[u] = (sons > 0) + max2 + (sons > 1) + max(0, sons - 2);

    // printf("%d %d\n", u, dp[u]);
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, t, m;

    cin >> n >> t >> m;
    for (int e = 0; e < n - 1; e++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    dfs(t, 0);

    int w = m;
    vector<int> path;
    while (w != t) {
        onPathTM[w] = true;
        path.push_back(w);
        w = parent[w];
    }
    onPathTM[w] = true;
    path.push_back(w);

    calcDp(t, 0);

    for (int i = path.size() - 1; i >= 0; i--) {
        int u = path[i];
        vector<int> sons;
        for (int v: adj[u]) {
            if (onPathTM[v])
                continue;
            sons.push_back(dpArb[v]);
        }
        sort(sons.begin(), sons.end());
        reverse(sons.begin(), sons.end());
        sons.push_back(0);

        for (int a = 1; a <= i + 1; a++) {
            dp[i][a] = INF;
            for (int d = 0; d <= a && d < (int)sons.size(); d++) {
                int cost = dp[i + 1][a - d + 1] + sons[d] + sons.size() - 1;
                dp[i][a] = min(dp[i][a], cost);
            }
            // printf("%d ", dp[i][a]);
        }
        // printf("\n");
    }

    cout << dp[0][1] << "\n";

    return 0;
}   

• Subtask 1: 0 / 20
• Subtask 2: 25 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35