Submission #1178682

#	Time	Username	Problem	Language	Result	Execution time	Memory
1178682		madamadam3	Closing Time (IOI23_closing)	C++20	9 / 100	1097 ms	47212 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; map<pi, int> weights;

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 v : adj[u]) { 
            if (v == parent[u]) continue;
            
            q.push(v);
            distances[v] = distances[u] + weights[{u, v}];
            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 v : adj[u]) {
            if (vis[s][v]) continue;

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

    return reachable;
}

int compute_value(int xL, int xR, int yL, int yR) {
    vector<int> costX(N, 0), costY(N, 0);
    
    costX[X] = 0;
    for (int i = X - 1; i >= xL; i--) {
        costX[i] = costX[i + 1] + weights[{i, i + 1}];
    }
    for (int i = X + 1; i <= xR; i++) {
        costX[i] = costX[i - 1] + weights[{i - 1, i}];
    }
    
    costY[Y] = 0;
    for (int i = Y - 1; i >= yL; i--) {
        costY[i] = costY[i + 1] + weights[{i, i + 1}];
    }
    for (int i = Y + 1; i <= yR; i++) {
        costY[i] = costY[i - 1] + weights[{i - 1, i}];
    }
    
    int total = 0;
    int unionL = min(xL, yL);
    int unionR = max(xR, yR);
    for (int i = unionL; i <= unionR; i++) {
        bool inX = (i >= xL && i <= xR);
        bool inY = (i >= yL && i <= yR);
        if (inX && inY) {
            total += max(costX[i], costY[i]);
        } else if (inX) {
            total += costX[i];
        } else if (inY) {
            total += costY[i];
        }
    }
    return total;
}

int solve_line() {
    int reachable = 0;
    if (X > Y) swap(X, Y);

    for (int xL = 0; xL <= X; xL++) {
        for (int xR = X; xR < N; xR++) {
            for (int yL = 0; yL <= Y; yL++) {
                for (int yR = Y; yR < N; yR++) {
                    int reached = (xR - xL + 1) + (yR - yL + 1);
                    // cout << "value: " << compute_value(xL, xR, yL, yR) << ", reached: " << reached << ", xrange = [" << xL << ", " << xR << "], yrange = [" << yL << ", " << yR << "]\n";
                    if (compute_value(xL, xR, yL, yR) <= K) {
                        reachable = max(reachable, reached);
                    }
                }
            }
        }
    }

    return reachable;
}

int bfs_mask(int mask) {
    int total_time = 0;
}

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); weights.clear();
    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(V[i]);
        adj[V[i]].push_back(U[i]);
        weights[{U[i], V[i]}] = W[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) {
    //     // cout << "line\n";
    //     ans = solve_line();
    // } else if (N <= 3000) {
    //     ans = solve_small();
    // } else {
    //     ans = solve();
    // }

    ans = solve_line();
    return ans;
}

Compilation message (stderr)

closing.cpp: In function 'int bfs_mask(int)':
closing.cpp:158:1: warning: no return statement in function returning non-void [-Wreturn-type]
  158 | }
      | ^

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