Submission #448914

#	Time	Username	Problem	Language	Result	Execution time	Memory
448914		JovanB	Pipes (BOI13_pipes)	C++17	100 / 100	264 ms	23980 KiB

pipes

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

using ll = long long;
using ld = long double;

const int N = 100000;
const int M = 500000;

ll cap[N+5];
vector <pair <int, int>> graf[N+5];
int deg[N+5];
bool bio[N+5];
ll sol[M+5];

pair <int, int> f[N+5][2];

void idi(int v, int lst, int root){
    if(v == root && lst != 0) return;
    int was = 0;
    for(auto pr : graf[v]){
        int c = pr.first;
        if(deg[c] <= 0) continue;
        if(v == root){
            f[v][was++] = pr;
        }
        else{
            if(c == lst) f[v][0] = pr;
            else f[v][1] = pr;
        }
    }
    idi(f[v][1].first, v, root);
}

int main(){
    ios_base::sync_with_stdio(false), cin.tie(0);
    cout.precision(10);
    cout << fixed;

    int n, m;
    cin >> n >> m;
    for(int i=1; i<=n; i++) cin >> cap[i];
    for(int i=1; i<=m; i++){
        int a, b;
        cin >> a >> b;
        graf[a].push_back({b, i});
        graf[b].push_back({a, i});
        deg[a]++;
        deg[b]++;
    }
    if(m > n){
        cout << "0\n";
        return 0;
    }
    queue <int> q;
    for(int i=1; i<=n; i++){
        if(deg[i] == 1){
            q.push(i);
        }
    }
    int ost = n;
    while(!q.empty()){
        int v = q.front();
        q.pop();
        ost--;
        bio[v] = 1;
        deg[v] = 0;
        for(auto pr : graf[v]){
            int c = pr.first, ind = pr.second;
            if(bio[c]) continue;
            sol[ind] = cap[v];
            cap[v] = 0;
            cap[c] -= sol[ind];
            deg[c]--;
            if(deg[c] == 1){
                q.push(c);
            }
        }
    }
    if(ost > 0 && ost%2 == 0){
        cout << "0\n";
        return 0;
    }
    if(ost > 0){
        int beg = 1;
        for(int i=1; i<=n; i++){
            if(deg[i] > 0) beg = i;
        }
        idi(beg, 0, beg);
        int v = f[beg][1].first;
        while(v != beg){
            sol[f[v][1].second] = cap[v] - sol[f[v][0].second];
            v = f[v][1].first;
        }
        ll dif = cap[v] - sol[f[beg][0].second];
        if(dif%2){
            cout << "0\n";
            return 0;
        }
        sol[f[beg][1].second] = dif/2;
        v = f[beg][1].first;
        while(v != beg){
            sol[f[v][1].second] = cap[v] - sol[f[v][0].second];
            v = f[v][1].first;
        }
    }
    for(int i=1; i<=m; i++) cout << 2*sol[i] << "\n";
    return 0;
}

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