Submission #673486

#	Time	Username	Problem	Language	Result	Execution time	Memory
673486		Lobo	Pipes (BOI13_pipes)	C++17	65 / 100	188 ms	52276 KiB

pipes

#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
const int maxn = 5e5+10;

int n, m, c[maxn], ans[maxn], gr[maxn];
vector<pair<int,int>> g[maxn], g1[maxn];
int sm = 0;
vector<int> vrt;
void dfs(int u, int ant, int cnt) {
    sm+= cnt*c[u];
    auto V = g1[u][0];
    if(V.fr == ant) V = g1[u][1];
    int v = V.fr;
    int id = V.sc;
    if(v == vrt[0]) return;
    dfs(v,u,cnt*-1);
}

void dfs1(int u, int ant, int cnt) {
    auto V = g1[u][0];
    if(V.fr == ant) V = g1[u][1];
    int v = V.fr;
    int id = V.sc;
    ans[id] = cnt*sm;
    if(v == vrt[0]) return;
    dfs1(v,u,cnt*-1);
}

void solve() {
    cin >> n >> m;
    for(int i = 1; i <= n; i++) {
        cin >> c[i];
    }
    for(int i = 1; i <= m; i++) {
        int u,v; cin >> u >> v;
        g[u].pb(mp(v,i));
        g[v].pb(mp(u,i));
        gr[u]++;
        gr[v]++;
    }

    if(m > n) {
        cout << 0 << endl;
        return;
    }
    queue<int> q;
    for(int i = 1; i <= n; i++) {
        if(gr[i] == 1) q.push(i);
    }

    while(q.size()) {
        int u = q.front(); q.pop();
        gr[u] = -1;
        for(auto V : g[u]) {
            int v = V.fr;
            int id = V.sc;
            if(gr[v] == -1) continue;
            ans[id] = 2*c[u];
            c[v]-= c[u];
            if(--gr[v] == 1) q.push(v);
        }
    }

    if(m == n) {
        for(int i = 1; i <= n; i++) {
            if(gr[i] != -1) {
                vrt.pb(i);
                for(auto V : g[i]) {
                    if(gr[V.fr] != -1) {
                        g1[i].pb(V);
                    }
                }
            }
        }
        if(vrt.size()%2 == 1) {
            dfs(vrt[0],-1,-1);
            dfs1(vrt[0],-1,1);
        }

    }

    for(int i = 1; i <= m; i++) {
        cout << ans[i] << endl;
    }
}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

Compilation message (stderr)

pipes.cpp: In function 'void dfs(long long int, long long int, long long int)':
pipes.cpp:24:9: warning: unused variable 'id' [-Wunused-variable]
   24 |     int id = V.sc;
      |         ^~

• Subtask 1: 30 / 30
• Subtask 2: 35 / 70