Submission #1174751

#	Time	Username	Problem	Language	Result	Execution time	Memory
1174751		vicvic	Pipes (BOI13_pipes)	C++20	74.07 / 100	245 ms	68536 KiB

pipes

#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <queue>
#include <cstdint>
#include <functional>
#define int long long
using namespace std;
int n, m;
set <pair <int, int>> adj[100005];
int c[100005], viz[100005], ans[100005], suf[100005];
vector <int> cycle_edge, cycle;
queue <int> coada;
int32_t main ()
{
    ios :: sync_with_stdio (0);
    cin.tie (nullptr);
    cin >> n >> m;
    for (int i=1;i<=n;i++)
    {
        cin >> c[i];
    }
    for (int i=1;i<=m;i++)
    {
        int x, y;
        cin >> x >> y;
        adj[x].insert ({y, i});
        adj[y].insert ({x, i});
    }
    if (m>n)
    {
        cout << "0\n";
        return 0;
    }
    for (int i=1;i<=n;i++)
    {
        if (adj[i].size()<2)
        {
            coada.push (i);
            viz[i]=1;
        }
    }
    int cnt=0;
    while (!coada.empty())
    {
        cnt++;
        auto chestie=coada.front();
        coada.pop();
        auto neighbour=*adj[chestie].begin();
        c[neighbour.first]-=c[chestie];
        ans[neighbour.second]+=c[chestie];
        adj[neighbour.first].erase ({chestie, neighbour.second});
        if (adj[neighbour.first].size()<2 && !viz[neighbour.first]) coada.push (neighbour.first), viz[neighbour.first]=1;
    }
    if ((n-cnt)%2==0)
    {
        cout << "0\n";
        return 0;
    }
    function <void (int)> dfs = [&] (int nod)
    {
        cycle.push_back (nod);
        for (auto chestie : adj[nod])
        {
            if (viz[chestie.first])
                continue;
            viz[chestie.first]=1;
            cycle_edge.push_back (chestie.second);
            dfs (chestie.first);
        }
    };
    int start=0;
    for (int i=1;i<=n;i++)
    {
        if (!viz[i])
            start=i;
    }
    viz[start]=1;
    if (start) dfs (start);
    int sz=cycle.size();
    for (int i=sz-1;i>=0;i--)
        suf[i]=c[cycle[i]]-suf[i+1];
    int pre=0;
    for (int i=0;i<sz;i++)
    {
        pre=c[cycle[i]]-pre;
        ans[cycle_edge[i]]=(pre+suf[i+1])/2;
    }
    for (int i=1;i<=m;i++)
    {
        cout << ans[i]*2 << "\n";
    }
    return 0;
}

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