Submission #816032

#	Time	Username	Problem	Language	Result	Execution time	Memory
816032		QwertyPi	Pipes (BOI13_pipes)	C++14	70.19 / 100	589 ms	131072 KiB

pipes

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

const int MAXN = 1e5 + 11;
const int MAXM = 5e5 + 11;

struct edge{
    int u, v, w;
    int exc(int x){
        return u + v - x;
    }
};
vector<edge> E;
set<int> G[MAXN];
int a[MAXN], b[MAXN], c[MAXN];

int32_t main(){
    cin.tie(0); cout.tie(0)->sync_with_stdio(false);
    int n, m; cin >> n >> m;
    for(int i = 1; i <= n; i++) cin >> a[i];
    int s = accumulate(a + 1, a + n + 1, 0LL);
    if(s % 2 == 1){
        cout << 0 << endl;
        return 0;
    }
    for(int i = 0; i < m; i++){
        int u, v; cin >> u >> v;
        E.push_back({u, v, 0});
        G[u].insert(i);
        G[v].insert(i);
    }

    vector<int> d1;
    for(int i = 1; i <= n; i++){
        if(G[i].size() == 1) d1.push_back(i);
    }

    while(!d1.empty()){
        int v = d1.back(); d1.pop_back();
        if(G[v].empty()) continue;
        for(auto e : G[v]){
            int u = E[e].u + E[e].v - v;
            G[u].erase(e);
            if(G[u].size() == 1) d1.push_back(u);
        }
        for(auto e : G[v]){
            c[e] = (a[v] - b[v]) * 2;
            b[E[e].u] += c[e] / 2;
            b[E[e].v] += c[e] / 2;
        }
        G[v].clear();
    }

    int node = 0, x = -1;
    for(int i = 1; i <= n; i++){
        assert(G[i].size() != 1);
        if(G[i].size() == 2){
            node++; x = i;
        }else if(G[i].size() > 2){
            cout << 0 << endl;
            return 0;
        }
    }

    if(node > 0 && node % 2 == 0){
        cout << 0 << endl;
        return 0;
    }

    if(node >= 3){
        vector<int> V, paths;
        V.push_back(x); paths.push_back(E[*G[x].begin()].u);
        x = E[*G[x].begin()].u;
        for(int i = 1; i < node; i++){
            V.push_back(x); paths.push_back(E[*G[x].begin()].exc(x) == V[i - 1] ? E[*--G[x].end()].exc(x) : E[*G[x].begin()].exc(x));
        }
        vector<int> tmp; tmp.push_back(0); for(int i = 1; i < node; i++) tmp.push_back((a[V[i]] - b[V[i]]) * 2 - tmp.back());
        int d = ((a[V[0]] - b[V[0]]) * 2 - tmp[0] - tmp[node - 1]) / 2;
        tmp.clear(); tmp.push_back(d); for(int i = 1; i < node; i++) tmp.push_back((a[V[i]] - b[V[i]]) * 2 - tmp.back());
        for(int i = 0; i < node; i++) c[paths[i]] = tmp[i];
    }

    for(int i = 0; i < m; i++){
        cout << c[i] << '\n';
    }
}

• Subtask 1: 30 / 30
• Subtask 2: 40.18518518518518 / 70