Submission #885163

#	Time	Username	Problem	Language	Result	Execution time	Memory
885163		12345678	Pipes (BOI13_pipes)	C++17	100 / 100	103 ms	37564 KiB

pipes

#include <bits/stdc++.h>

using namespace std;

#define ll long long

const int nx=5e5+5;
int n, m, h[nx], u, v, sz, res[nx], vs[nx], cy[nx], pa[nx], pidx[nx], cnt, lst;
vector<pair<int, int>> d[nx], c;

void dfs(int u, int p, int idx)
{
    vs[u]=1; pa[u]=p; pidx[u]=idx;
    for (auto [v, id]:d[u]) 
    {
        if (v==p||cy[v]) continue;
        if (!vs[v]) dfs(v, u, id);
        else
        {
            int tmp=u;
            while (tmp!=v) cy[tmp]=1, c.push_back({tmp, pidx[tmp]}), tmp=pa[tmp], cnt++;
            cy[v]=1; cnt++; c.push_back({v, id});
        }
    }
    if (idx==-1||m==n) return;
    res[idx]=2*h[u];
    h[p]-=h[u];
}

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin>>n>>m;
    for (int i=1; i<=n; i++) cin>>h[i];
    for (int i=1; i<=m; i++) cin>>u>>v, d[u].push_back({v, i}), d[v].push_back({u, i});
    if (m>n) {cout<<0; return 0;}
    dfs(1, 1, -1);
    if (cnt%2==0&&cnt!=0) {cout<<0; return 0;}
    if (m<n) for (int i=1; i<n; i++) cout<<res[i]<<'\n';
    else
    {
        m=n-1;
        for (int i=1; i<=n; i++) vs[i]=0;
        for (auto [x, y]:c) dfs(x, x, -1);
        int l=-1e9, r=1e9;
        while (l<=r)
        {
            vector<int> t(c.size());
            int md=(l+r+1)/2;
            //cout<<"here "<<l<<' '<<r<<' '<<md<<'\n';
            lst=md;
            t[0]+=md;
            t[c.size()-1]+=md;
            res[c[c.size()-1].second]=2*md;
            for (int i=1; i<c.size(); i++) t[i]+=(h[c[i-1].first]-t[i-1]), res[c[i-1].second]=2*(h[c[i-1].first]-t[i-1]);
            if (t[c.size()-1]==h[c[c.size()-1].first]) break;
            if (t[c.size()-1]>=h[c[c.size()-1].first]) r=md-1;
            else l=md;
        }
        //for (int i=1; i<=n; i++) if (cy[i]) cout<<i<<' '<<h[i]<<'\n';
        for (int i=1; i<=m+1; i++) cout<<res[i]<<'\n';
    }
}

/*
4 4
2 0 2 2
1 2
1 3
2 3
3 4
*/

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:55:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |             for (int i=1; i<c.size(); i++) t[i]+=(h[c[i-1].first]-t[i-1]), res[c[i-1].second]=2*(h[c[i-1].first]-t[i-1]);
      |                           ~^~~~~~~~~

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