Cod sursa(job #3326564)

Utilizator Gabriel_DaescuDaescu Gabriel Florin Gabriel_Daescu Data 29 noiembrie 2025 14:08:29
Problema Obiective Scor 5
Compilator cpp-64 Status done
Runda Arhiva de probleme Marime 4.04 kb
#include <fstream>
#include <vector>
#include <stack>
#define NMAX 35002
using namespace std;
ifstream  fin("obiective.in");
ofstream fout("obiective.out");
int N,M,T,nrctc,c[NMAX],viz[NMAX],dist[NMAX],nivel[NMAX],tata[NMAX];
vector<int> graph[NMAX],graph_tr[NMAX];
vector<pair<int,int>> graph_ctc[NMAX];
stack<int> stiva;

void citire()
{
    fin>>N>>M;

    int u,v;
    for(int i=1; i<=M; i++)
    {
        fin>>u>>v;
        graph[u].push_back(v);
        graph_tr[v].push_back(u);
    }

    fin>>T;
}

void DFS1(int nod)
{
    viz[nod]=1;
    for(int i=0; i<graph[nod].size(); i++)
    {
        int next_nod=graph[nod][i];
        if(!viz[next_nod])
        {
            DFS1(next_nod);
        }
    }
    stiva.push(nod);
}

void DFS2(int nod)
{
    c[nod]=nrctc;
    viz[nod]=0;
    for(int i=0; i<graph_tr[nod].size(); i++)
    {
        int next_nod=graph_tr[nod][i];
        if(viz[next_nod])
        {
            DFS2(next_nod);
        }
    }
}

// adauga muchie in graph_ctc dar deduplica si pastreaza costul minim
void add_edge_ctc(int u, int v, int cost) {
    // caut daca exista deja v in lista lui u
    for (auto &p : graph_ctc[u]) {
        if (p.first == v) {
            if (cost < p.second) p.second = cost;
            return;
        }
    }
    graph_ctc[u].push_back({v, cost});
}

void DFS_arb(int nod, int parent)
{
    tata[nod]=parent;
    for(int i=0; i<graph_ctc[nod].size(); i++)
    {
        int next_nod=graph_ctc[nod][i].first;
        int cost=graph_ctc[nod][i].second;

        if(next_nod!=parent)
        {
            nivel[next_nod]=nivel[nod]+1;
            dist[next_nod]=dist[nod]+cost;
            DFS_arb(next_nod,nod);
        }
    }
}

int LCA(int a, int b)
{
    while(a!=b)
    {
       if(nivel[a]>nivel[b])
       {
           a=tata[a];
       }
       else
       {
           b=tata[b];
       }
    }
    return a;
}

int main()
{
    citire();

    // Kosaraju - prima faza
    for(int i=1; i<=N; i++)
    {
        if(!viz[i])
        {
            DFS1(i);
        }
    }

    // Kosaraju - a doua faza
    nrctc=0;
    while(!stiva.empty())
    {
        int nod=stiva.top();
        stiva.pop();

        if(viz[nod])
        {
            nrctc++;
            DFS2(nod);
        }
    }

    // Construim graful componentelor, deduplicand muchiile si pastrand costul minim
    for(int i=1; i<=N; i++)
    {
        for(int j=0; j<graph[i].size(); j++)
        {
            int u=i;
            int v=graph[i][j];
            if(c[u]!=c[v])
            {
                // din c[u] catre c[v] cost 0 (directa)
                add_edge_ctc(c[u], c[v], 0);
                // invers: din c[v] catre c[u] cost 1
                add_edge_ctc(c[v], c[u], 1);
            }
        }
    }

    // initializari pentru componente
    for (int i = 1; i <= nrctc; ++i) {
        nivel[i] = 0;
        dist[i] = 0;
        tata[i] = 0;
    }

    // parcurgem fiecare componenta conexa neorientata (sigur ca e una, dar asta e siguranta)
    for (int start = 1; start <= nrctc; ++start) {
        if (tata[start] != 0) continue; // deja vizitat
        tata[start] = start;
        nivel[start] = 0;
        dist[start] = 0;
        DFS_arb(start, start);
    }

    int g,m;
    for(int q=1; q<=T; q++)
    {
        fin>>g>>m;

        if(c[g]==c[m])
        {
            fout<< 0;
        }
        else
        {
            int cg = c[g], cm = c[m];
            int l = LCA(cg, cm);

            // calcul corect: cost de la L la B (jos) + cost de la A la L (sus)
            int cost_L_to_B = dist[cm] - dist[l];
            int up_edges_A_to_L = nivel[cg] - nivel[l];                // numarul de muchii urcate
            int cost_A_to_L_when_up = up_edges_A_to_L - (dist[cg] - dist[l]); // fiecare muchie urcata costa 1 - cost(muchie jos)
            int ans = cost_L_to_B + cost_A_to_L_when_up;

            fout<< ans;
        }
        fout<< "\n";
    }

    return 0;
}