Submission #998891

#	Time	Username	Problem	Language	Result	Execution time	Memory
998891		Wael	Closing Time (IOI23_closing)	C++17	26 / 100	1098 ms	69696 KiB

closing

#include "closing.h"
//#include "grader.cpp"
#include <bits/stdc++.h>
using namespace std;
using i64 = long long;

int max_score(int n, int x, int y, long long k, vector<int> U, vector<int> V, vector<int> W) {
    vector<vector<pair<int, int>>> adj(n);
    for (int i = 0; i < n - 1; ++i) {
        adj[U[i]].push_back({V[i], W[i]});
        adj[V[i]].push_back({U[i], W[i]});
    }

    vector<vector<i64>> dis(n, vector<i64>(2, 0));
    vector<vector<int>> next(n, vector<int>(2, -1));
    function<void(int, int, int)> dfs = [&](int u, int p, int t) {
        for (auto [v, w] : adj[u]) {
            if (v == p) continue;
            dis[v][t] = dis[u][t] + w;
            next[v][!t] = u;
            dfs(v, u, t);
        }
    };
    dfs(x, -1, 0);
    dfs(y, -1, 1);

    i64 pathCost = 0;
    vector<int> path, onPath(n, 0);
    int z = x;
    while (true) {
        path.push_back(z);
        onPath[z] = 1;
        pathCost += min(dis[z][0], dis[z][1]);
        if (z == y) {
            break;
        }
        z = next[z][0];
    }
    
    vector<pair<i64, int>> vec;
    vector<i64> one(n), two(n);
    for (int u = 0; u < n; ++u) {
        one[u] = min(dis[u][0], dis[u][1]);
        two[u] = max(dis[u][0], dis[u][1]);
        vec.push_back({two[u], u});
    }
    sort(vec.begin(), vec.end(), greater<pair<i64, int>>());

    vector<int> used(n, 0);
    auto work = [&](bool mark, i64 k) {
        int ret = 0;
        vector<int> vis = used;
        if (mark) {
            for (auto u : path) {
                if (vis[u] == 0) {
                    vis[u] = 1;
                    k -= one[u];
                    ++ret;
                }
            }
        } else {
            vis[x] = vis[y] = 1;
            ret = 2;
        }
        if (k < 0) {
            return (int)-1e9;
        }

        priority_queue<pair<i64, int>, vector<pair<i64, int>>, greater<pair<i64, int>>> pq;
        for (int u = 0; u < n; ++u) {
            bool found = 0;
            for (auto [v, w] : adj[u]) {
                found |= vis[v];
            }
            if (found) {
                pq.push({one[u], u});
            }
        }

        while (pq.size()) {
            auto [cost, u] = pq.top();
            pq.pop();
            if (cost > k) {
                break;
            }
            if (vis[u]) {
                continue;
            }

            vis[u] = 1;        
            k -= cost;
            ++ret;
            for (auto [v, w] : adj[u]) {
                pq.push({one[v], v});
            }
        }

        return ret;
    };

    auto canMark = [&](int u, i64 k, i64 pathCost) {
        pathCost -= (onPath[u] ? one[u] : 0);
        k -= two[u];
        return k >= pathCost;
    };

    int ans = 0;
    if (n <= 20) {
        for (int mask = 0; mask < (1 << n); ++mask) {
            fill(used.begin(), used.end(), 0);

            i64 curK = k;
            for (int j = 0; j < n; ++j) {
                if (mask & (1 << j)) {
                    used[j] = 1;
                    curK -= two[j];
                }
            }
            int cnt = __builtin_popcount(mask);
            ans = max(ans, work(cnt > 0, curK) + 2 * cnt);
        }
    } else {
        for (int c = 0; c <= n; ++c) {
            if (c) {
                ans = max(ans, work(1, k) + 2 * c);
            } else {
                ans = max(ans, work(0, k));
            }
            while (vec.size() && canMark(vec.back().second, k, pathCost) == 0) {
                vec.pop_back();
            }
            if (vec.size() == 0) {
                break;
            }
            auto [cost, u] = vec.back();
            vec.pop_back();
            used[u] = 1;
            pathCost -= (onPath[u] ? one[u] : 0);
            k -= two[u];
        }
    }

    return ans;
}

• Subtask 0: 0 / 0
• Subtask 1: 8 / 8
• Subtask 2: 9 / 9
• Subtask 3: 0 / 12
• Subtask 4: 0 / 14
• Subtask 5: 9 / 9
• Subtask 6: 0 / 11
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 17