Submission #1178470

#	Time	Username	Problem	Language	Result	Execution time	Memory
1178470		madamadam3	Closing Time (IOI23_closing)	C++20	0 / 100	31 ms	6720 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;
}

int solve_disconnected() {
    vi parent(N, -1);
    int reachable = 0;
    ll cur_sum = 0;

    priority_queue<pli> q;
    q.push({0LL, X});
    q.push({0LL, Y});

    while (!q.empty()) {
        ll dist = q.top().first, u = q.top().second;
        q.pop();
        if (dist + cur_sum > K) break;

        reachable++;
        cur_sum += dist;

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

            q.push({W[eid], v});
        }
    }

    return reachable;
}

int solve_line() {

}

int solve_small() {

}

int solve() {

}

/*
    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) {
    N = _N; X = _X; Y = _Y; U = _U; V = _V; for (int i = 0; i < N - 1; i++) W.push_back(ll(W[i]));
    adj.assign(N, vi());

    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 ans;
}

Compilation message (stderr)

closing.cpp: In function 'int solve_line()':
closing.cpp:71:1: warning: no return statement in function returning non-void [-Wreturn-type]
   71 | }
      | ^
closing.cpp: In function 'int solve_small()':
closing.cpp:75:1: warning: no return statement in function returning non-void [-Wreturn-type]
   75 | }
      | ^
closing.cpp: In function 'int solve()':
closing.cpp:79:1: warning: no return statement in function returning non-void [-Wreturn-type]
   79 | }
      | ^

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