Submission #78936

#	Time	Username	Problem	Language	Result	Execution time	Memory
78936		Charis02	Pipes (BOI13_pipes)	C++14	100 / 100	322 ms	29372 KiB

pipes

/*
solution is the same as described here: https://boi2013.informatik-olympiade.de/wp-content/uploads/2013/05/pipes-spoiler.pdf
*/

#include<iostream>
#include<stdio.h>
#include<vector>
#include<cmath>
#include<queue>
#include<string.h>
#include<map>
#include<set>
#include<algorithm>
#include<stack>
#define ll long long
#define pi pair < ll,ll >
#define mp(a,b) make_pair(a,b)
#define rep(i,a,b) for(int i = a;i < b;i++)
#define N 100004
#define INF 1e9+7

using namespace std;

ll n,m,ar[N],val[N],deg[N];
bool vis[N],cycle;
vector < vector < pi > > graph(N);
vector < pi > neo;

void solvetree(ll cur,ll par,ll edge)
{
    rep(i,0,graph[cur].size())
    {
        ll v = graph[cur][i].first;

        if(v == par)
            continue;

        solvetree(v,cur,graph[cur][i].second);

        ar[cur] -= val[graph[cur][i].second];
    }

    val[edge] = ar[cur];

    return;
}

int main()
{
    ios_base::sync_with_stdio(false);

    cin >> n >> m;

    rep(i,1,n+1)
    {
        cin >> ar[i];
    }

    rep(i,0,m)
    {
        ll a,b;
        cin >> a >> b;
        graph[a].push_back(mp(b,i));
        graph[b].push_back(mp(a,i));
    }

    if(m > n)
    {
        cout << 0 << endl;
        return 0;
    }
    else if(m == n-1)
    {
        solvetree(1,1,m);

        rep(i,0,m)
        {
            cout << 2*val[i] << endl;
        }
    }
    else
    {
        ll nodes = n;
        stack < pi > s;

        rep(i,1,n+1)
        {
            deg[i] = graph[i].size();

            if(deg[i] == 1)
            {
                vis[i] = true;
                s.push(mp(i,graph[i][0].second));
            }
        }

        while(!s.empty())
        {
            nodes--;
            ll cur = s.top().first;
            ll e = s.top().second;
            s.pop();
            deg[cur]--;

          //  cout << cur << " " << e << endl;
            val[e] = ar[cur];

       //     cout << deg[1] <<endl;

            rep(i,0,graph[cur].size())
            {
                ll v = graph[cur][i].first;

                if(deg[v] <= 1)
                    continue;

                ar[v] -= val[e];

                deg[v]--;
                graph[v].erase(find(graph[v].begin(),graph[v].end(),mp(cur,graph[cur][i].second)));

             //   cout << v << " " << deg[v] << endl;

                if(deg[v] == 1)
                {
                    vis[v] = true;
                    s.push(mp(v,graph[v][0].second));
                }
            }
        }

        ll st = 1;

        while(vis[st])
        {
            st++;
        }

        ll start = st;

        while(!vis[start])
        {
            pi potential;
            bool found = false;
            rep(i,0,graph[st].size())
            {
                ll v =  graph[st][i].first;

                if(!vis[v])
                {
                    if(v == start)
                    {
                        potential = mp(st,graph[st][i].second);
                        continue;
                    }

                    found = true;
                    neo.push_back(mp(st,graph[st][i].second));
                    vis[v] = true;
                    st = v;
                    break;
                }
            }

            if(!found)
            {
                vis[start] = true;
                neo.push_back(potential);
                st = start;
            }
        }

        if((neo.size())%2==0)
        {
            cout << 0 << endl;
        }
        else
        {
            ll s = 0;

            rep(i,0,neo.size())
            {
                s += ar[neo[i].first]*pow(-1,i%2);
            }

            val[neo[neo.size()-1].second] = s/2;
            val[neo[0].second] = ar[neo[0].first] - s/2;

            rep(i,1,neo.size()-1)
            {
                val[neo[i].second] =ar[neo[i].first]  - val[neo[i-1].second];
            }

            rep(i,0,m)
            {
                cout << 2*val[i] << endl;
            }
        }
    }

    return 0;
}

/*
3 3
1 3 2
1 2
1 3
2 3


4 4
1 3 2 0
4 1
1 2
1 3
2 3


5 5
1 3 2 -4 0
5 1
1 2
4 3
2 3
2 4
*/

Compilation message (stderr)

pipes.cpp: In function 'void solvetree(long long int, long long int, long long int)':
pipes.cpp:18:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep(i,a,b) for(int i = a;i < b;i++)
pipes.cpp:31:9:
     rep(i,0,graph[cur].size())
         ~~~~~~~~~~~~~~~~~~~~~       
pipes.cpp:31:5: note: in expansion of macro 'rep'
     rep(i,0,graph[cur].size())
     ^~~
pipes.cpp: In function 'int main()':
pipes.cpp:18:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep(i,a,b) for(int i = a;i < b;i++)
pipes.cpp:110:17:
             rep(i,0,graph[cur].size())
                 ~~~~~~~~~~~~~~~~~~~~~
pipes.cpp:110:13: note: in expansion of macro 'rep'
             rep(i,0,graph[cur].size())
             ^~~
pipes.cpp:18:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep(i,a,b) for(int i = a;i < b;i++)
pipes.cpp:145:17:
             rep(i,0,graph[st].size())
                 ~~~~~~~~~~~~~~~~~~~~
pipes.cpp:145:13: note: in expansion of macro 'rep'
             rep(i,0,graph[st].size())
             ^~~
pipes.cpp:18:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep(i,a,b) for(int i = a;i < b;i++)
pipes.cpp:181:17:
             rep(i,0,neo.size())
                 ~~~~~~~~~~~~~~      
pipes.cpp:181:13: note: in expansion of macro 'rep'
             rep(i,0,neo.size())
             ^~~
pipes.cpp:18:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep(i,a,b) for(int i = a;i < b;i++)
pipes.cpp:189:17:
             rep(i,1,neo.size()-1)
                 ~~~~~~~~~~~~~~~~    
pipes.cpp:189:13: note: in expansion of macro 'rep'
             rep(i,1,neo.size()-1)
             ^~~

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