Submission #447748

#	Time	Username	Problem	Language	Result	Execution time	Memory
447748		prvocislo	Pipes (BOI13_pipes)	C++17	100 / 100	84 ms	19424 KiB

pipes

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

void end() 
{ 
    cout << 0 << endl;
    exit(0);
}
const int maxn = 1e5 + 5;
vector<pair<int, int> > g[maxn];
int deg[maxn], vis[maxn], n[maxn], e[maxn];
ll sum[maxn*2];
vector<int> cy;
void dfs(int u, int p, int st)
{
    if (u == st && p != -1) return;
    sum[cy.size()] = n[u];
    for (pair<int, int> v : g[u]) if (!vis[v.first] && v.first != p) 
    {
        cy.push_back(v.second);
        dfs(v.first, u, st);
        if (u == st) return;
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N, M;
    cin >> N >> M;
    if (M > N) end();
    for (int i = 0; i < N; i++) cin >> n[i];
    for (int i = 0, u, v; i < M; i++) 
    {
        cin >> u >> v;
        g[--u].push_back({--v, i}), g[v].push_back({u, i});
        deg[u]++, deg[v]++;
    }
    vector<int> stk;
    for (int i = 0; i < N; i++) if (deg[i] == 1) stk.push_back(i);
    while (!stk.empty())
    {
        int u = stk.back(); stk.pop_back();
        vis[u] = true;
        for (pair<int, int> v : g[u]) if (!vis[v.first])
        {
            e[v.second] = n[u]*2;
            n[v.first] -= n[u];
            deg[v.first]--;
            if (deg[v.first] == 1) stk.push_back(v.first);
        }
    }
    if (N == M) // ostal nam cyklus
    {
        for (int i = 0; i < N; i++) if (!vis[i])
        {
            dfs(i, -1, i);
            break;
        }
        int k = cy.size();
        if (!(k&1)) end();
        for (int i = k; i < 2*k; i++) sum[i] = sum[i-cy.size()];
        for (int i = 0; i < 2*k; i++) if (i&1) sum[i] *= -1;
        for (int i = 1; i < 2*k; i++) sum[i] += sum[i-1];
        for (int i = 0; i < k; i++)
        {
            e[cy[i]] = sum[i+k]-sum[i];
            if (!(i&1)) e[cy[i]] *= -1;
        }
    }
    for (int i = 0; i < M; i++) cout << e[i] << "\n";
    return 0;
}

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