제출 #1178539

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1178539		madamadam3	봉쇄 시간 (IOI23_closing)	C++20	8 / 100	69 ms	22964 KiB

closing

#include "closing.h"
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using pi = pair<int, int>;
using pli = pair<ll, int>;

int N, X, Y; ll K;
vi U, V; vl W;
vvi adj;

vi compute_distances(int start) {
    vi distances(N, 0);
    vi parent(N, -1);

    queue<int> q;
    q.push(start);

    while (!q.empty()) {
        int u = q.front();
        q.pop();

        for (int eid : adj[u]) {
            int v = U[eid] == u ? V[eid] : U[eid];
            if (v == parent[u]) continue;
            
            q.push(v);
            distances[v] = distances[u] + W[eid];
            parent[v] = u;
        }
    }

    return distances;
}

struct BFSNode {
    int u, s; ll dist;

    BFSNode(int u, int s, ll dist) {
        this->u = u;
        this->s = s;
        this->dist = dist;
    }

    bool operator<(const BFSNode &other) const {
        return dist < other.dist;
    }

    bool operator>(const BFSNode &other) const {
        return dist > other.dist;
    }
};

int solve_disconnected() {
    vector<vector<bool>> vis(2, vector<bool>(N, false));
    vl tim(N+1, 0LL);

    int reachable = 0;
    ll cur_sum = 0;

    priority_queue<BFSNode, vector<BFSNode>, greater<BFSNode>> q;
    q.push(BFSNode(X, 0, 0LL));
    q.push(BFSNode(Y, 1, 0LL));

    while (!q.empty()) {
        BFSNode cur = q.top();
        int u = cur.u, s = cur.s;
        ll dist = cur.dist;
        q.pop();

        if (vis[s][u]) continue;
        vis[s][u] = true;

        // cout << "Node = " << u << " Source = " << s << " Dist = " << dist << "\n";
        // cout << "Current Sum = " << cur_sum << "\n";

        if (dist + cur_sum > K) continue;

        reachable++;
        cur_sum += dist;
        tim[u] += dist;

        for (int eid : adj[u]) {
            int v = U[eid] == u ? V[eid] : U[eid];
            if (vis[s][v]) continue;

            ll ndist = tim[u] + W[eid] - tim[v];
            // cout << "Neighbour = " << v << " Cost = " << ndist << "\n";
            q.push(BFSNode(v, cur.s, max(0LL, ndist)));
        }
    }

    return reachable;
}

int solve_line() {
    int reachable = 0;
    return reachable;
}

int solve_small() {
    int reachable = 0;
    return reachable;
}

int solve() {
    int reachable = 0;
    return reachable;
}

/*
    N: number of cities <= 200k
    X, Y: 2 cities of interest 0 < X != Y < N
    K: maximum allowed sum of closing times <= 10^18
    U, V: road[j] = (U[j], V[j])
    W: W[j] = length of road[W]
*/
int max_score(int _N, int _X, int _Y, ll _K, vi _U, vi _V, vi _W) {
    W.resize(0);
    N = _N; X = _X; Y = _Y; K = _K; U = _U; V = _V; for (int i = 0; i < N - 1; i++) W.push_back(ll(_W[i]));
    adj.assign(N, vi());

    // cout << "N = " << N << " X = " << X << " Y = " << Y << " K = " << K << "\n";

    bool line = true;
    for (int i = 0; i < N - 1; i++) {
        adj[U[i]].push_back(i);
        adj[V[i]].push_back(i);

        line = line && max(U[i], V[i]) == min(U[i], V[i]) + 1;
    }

    vi distX = compute_distances(X), distY = compute_distances(Y);
    
    int ans = 0;
    if (distX[Y] > 2 * K) {
        ans = solve_disconnected();
    } else if (line) {
        ans = solve_line();
    } else if (N <= 3000) {
        ans = solve_small();
    } else {
        ans = solve();
    }

    return solve_disconnected();
}

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