Cod sursa(job #2313925)

Utilizator BlaugranasEnal Gemaledin Blaugranas Data 7 ianuarie 2019 17:26:39
Problema 2SAT Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 3.35 kb
#include<fstream>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
#define N 200001
int variables,expressions;
vector<int> var_adj[N],var_adj_t[N],vtc(N),value(N,-1),scc_in_deg(N,0);
vector<vector<int>> sccs;
inline int abs(const int x)
{
    return (x < 0) ? -x : +x;
}
inline int idx(const int x)
{
    return (x < 0) ? abs(x) + variables : x;
}
inline int non(const int x)
{
    return (x > variables) ? x - variables : x + variables;
}
void DFP(int n, vector <int>& used, vector <int>& discover)
{
    vector <int>::iterator it;
    used[n] = 1;
    for (it = var_adj[n].begin(); it != var_adj[n].end(); ++ it)
        if (!used[*it])
            DFP(*it, used, discover);
    discover.push_back(n);
}
void DFM(int n, vector <int>& used, vector <int>& scc)
{
    vector <int>::iterator it;
    used[n] = 1;
    scc.push_back(n);
    for (it = var_adj_t[n].begin(); it != var_adj_t[n].end(); ++ it)
        if (!used[*it])
            DFM(*it, used, scc);
}
void compute_sccs(void)
{
    vector <int> used(N), discover, scc;
    used.assign(used.size(), 0);
    for (int i = 1; i <= variables * 2; ++ i)
        if (!used[i])
            DFP(i, used, discover);
    used.assign(used.size(), 0);
    vector <int>::reverse_iterator it;
    for (it = discover.rbegin(); it != discover.rend(); ++ it)
        if (!used[*it])
        {
            scc.clear();
            DFM(*it, used, scc);
            for (vector <int>::iterator it2 = scc.begin(); it2 != scc.end(); ++ it2)
                vtc[*it2] = sccs.size();
            sccs.push_back(scc);
        }
}
int main()
{
    ifstream in("2sat.in");
    ofstream out("2sat.out");
    in>>variables>>expressions;
    for (int i = 0; i < expressions; ++ i)
    {
        int x, y;
        in>>x>>y;
        var_adj[non(idx(x))].push_back(idx(y));
        var_adj_t[idx(y)].push_back(non(idx(x)));
        var_adj[non(idx(y))].push_back(idx(x));
        var_adj_t[idx(x)].push_back(non(idx(y)));
    }
    compute_sccs();
    int impossible = false;
    for (int x = 1; x <= variables; ++ x)
        if (vtc[x] == vtc[x + variables])
            impossible = true;
    if (!impossible)
    {
        for (int x = 1; x <= variables * 2; ++ x)
        {
            vector <int>::iterator it;
            for (it = var_adj[x].begin(); it != var_adj[x].end(); ++ it)
                if (vtc[x] != vtc[*it])
                    scc_in_deg[ vtc[*it] ] ++;
        }
        queue <int> Q;
        for (int idx = 0; idx < (int) sccs.size(); ++ idx)
            if (scc_in_deg[idx] == 0)
                Q.push(idx);
        while (!Q.empty())
        {
            int idx = Q.front();
            Q.pop();
            vector <int>::iterator it, i, j;
            for (it = sccs[idx].begin(); it != sccs[idx].end(); ++ it)
            {
                int x = (*it > variables) ? *it - variables : *it;
                if (value[x] == -1)
                    value[x] = (*it <= variables) ? 0 : 1;
            }
            for (i = sccs[idx].begin(); i != sccs[idx].end(); ++ i)
            {
                for (j = var_adj[*i].begin(); j != var_adj[*i].end(); ++ j)
                    if (vtc[*i] != vtc[*j])
                        if ((-- scc_in_deg[ vtc[*j] ]) == 0)
                            Q.push(vtc[*j]);
            }
        }
        for (int i = 1; i <= variables; ++ i)
            out << value[i] << " ";
    }
    else
        out << -1;
}