Cod sursa(job #2122439)

Utilizator andreigasparoviciAndrei Gasparovici andreigasparovici Data 5 februarie 2018 08:15:34
Problema Sortare topologica Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.08 kb
#include <fstream>
#include <algorithm>
#include <iostream>
#include <bitset>
#include <vector>
#include <stack>

using namespace std;

const int NMAX = 50005;

int n, m;
int globalIndex;
int index[NMAX], lowlink[NMAX];

vector<int> g[NMAX];
vector<int> topsort;

stack<int> st;
bitset<NMAX> v;

void read() {
  ifstream in("sortaret.in");
  in >> n >> m;
  int x, y;
  for (int i = 1; i <= m; i++) {
    in >> x >> y;
    g[x].push_back(y);
  }
}

void dfs(int x) {
  v[x] = 1;
  st.push(x);
  index[x] = lowlink[x] = ++globalIndex;

  for (int y : g[x]) {
    if (!index[y]) {
      dfs(y);
      lowlink[x] = min(lowlink[x], lowlink[y]);
    } else if (v[y]) {
      lowlink[x] = min(lowlink[x], index[y]);
    }
  }

  if (lowlink[x] == index[x]) {
    int y;
    do {
      y = st.top();
      st.pop();
      v[x] = 0;
      topsort.push_back(y);
    } while (y != x);
  }
}

int main() {
  read();

  for (int i = 1; i <= n; i++)
    if (!index[i])
      dfs(i);

  ofstream out("sortaret.out");
  reverse(topsort.begin(), topsort.end());
  for (int x : topsort)
    out << x << " ";

  return 0;
}