Submission #1266665

#	Time	Username	Problem	Language	Result	Execution time	Memory
1266665		SnowRaven52	Pipes (BOI13_pipes)	C++20	44.07 / 100	109 ms	21584 KiB

pipes

#include <bits/stdc++.h>
using namespace std;

int main() {
  // freopen("main.in", "r", stdin);
	// freopen(".out", "w", stdout);
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, M; cin >> N >> M;
    vector<long long> s(N + 1);
    for (int i = 1; i <= N; i++) cin >> s[i];
    vector<pair<int,int>> edges(M + 1);
    vector<vector<pair<int,int>>> adj(N + 1);
    vector<int> deg(N + 1, 0);
    for (int i = 1; i <= M; i++) {
        int u, v; cin >> u >> v;
        edges[i] = {u, v};
        adj[u].push_back({v, i});
        adj[v].push_back({u, i});
        deg[u]++; deg[v]++;
    }

    if (M > N) { cout << 0 << endl; return 0; }

    vector<char> deadE(M + 1, 0), deadV(N + 1, 0);
    vector<long long> w(M + 1, 0);
    queue<int> q;
    for (int i = 1; i <= N; i++) if (deg[i] == 1) q.push(i);

    while (!q.empty()) {
        int v = q.front(); q.pop();
        if (deadV[v]) continue;
        int eid = -1, u = -1;
        for (auto [to, e] : adj[v]) if (!deadE[e]) { u = to; eid = e; break; }
        if (eid == -1) { deadV[v] = 1; continue; }
        w[eid] = s[v];
        s[u] -= w[eid];
        deadE[eid] = 1;
        deg[v]--; deg[u]--;
        deadV[v] = 1;
        if (deg[u] == 1) q.push(u);
    }

    int aliveE = 0, start = -1, aliveV = 0;
    for (int e = 1; e <= M; e++) if (!deadE[e]) aliveE++;
    for (int i = 1; i <= N; i++) if (!deadV[i] && deg[i] > 0) { aliveV++; if (start == -1) start = i; }

    if (aliveE == 0) {
        for (int i = 1; i <= M; i++) cout << w[i] << endl;
        return 0;
    }

    for (int i = 1; i <= N; i++) if (!deadV[i] && deg[i] != 2) { cout << 0 << '\n'; return 0; }
    if (aliveE != aliveV) { cout << 0 << endl; return 0; }

    vector<int> cycV, cycE;
    int v = start, prev = -1, cntE = 0;
    do {
        cycV.push_back(v);
        int ne = -1, nv = -1;
        for (auto [to, e] : adj[v]) if (!deadE[e] && e != prev) { ne = e; nv = to; break; }
        if (ne == -1) { cout << 0 << endl; return 0; }
        cycE.push_back(ne);
        prev = ne; v = nv; cntE++;
    } while (v != start && cntE <= aliveE);
    if (v != start || (int)cycE.size() != aliveE) { cout << 0 << '\n'; return 0; }

    int K = (int)cycV.size();
    if (K % 2 == 0) { cout << 0 << endl; return 0; }

    long long alt = 0;
    for (int i = 0; i < K; i++) alt += (i % 2 ? -s[cycV[i]] : s[cycV[i]]);
    long long lastW = alt / 2;
    w[cycE.back()] = lastW;
    long long prevW = lastW;
    for (int i = 0; i < K - 1; i++) {
        long long curW = s[cycV[i]] - prevW;
        w[cycE[i]] = curW;
        prevW = curW;
    }

    for (int i = 1; i <= M; i++) cout << w[i] << endl;
    return 0;
}

• Subtask 1: 0 / 30
• Subtask 2: 44.0741 / 70