How to use

SCCTarjan

in

org.kframework.utils.algorithms

  public static void main(String[] args) {
    @SuppressWarnings("unchecked")
    List<Integer>[] g = new List[10];
    for (int i = 0; i < g.length; i++) {
      g[i] = new ArrayList<>();
    }
    g[0].add(1);
    g[0].add(2);
    g[2].add(1);
    g[1].add(2);
    g[3].add(2);
    g[4].add(3);
    g[5].add(4);
    g[6].add(5);
    g[7].add(6);
    g[8].add(9);
    g[9].add(7);


    List<List<Integer>> components = new SCCTarjan().scc(g);
    System.out.println(components);
  }
}

public List<List<Integer>> scc(List<Integer>[] graph) {
  int n = graph.length;
  this.graph = graph;
  lowlink = new int[n];
  used = new boolean[n];
  stack = new ArrayList<>();
  components = new ArrayList<>();
  for (int u = 0; u < n; u++)
    if (!used[u])
      dfs(u);
  return components;
}

List<List<Integer>> components = new SCCTarjan().scc(predecessors);

void dfs(int u) {
  lowlink[u] = time++;
  used[u] = true;
  stack.add(u);
  boolean isComponentRoot = true;
  for (int v : graph[u]) {
    if (!used[v])
      dfs(v);
    if (lowlink[u] > lowlink[v]) {
      lowlink[u] = lowlink[v];
      isComponentRoot = false;
    }
  }
  if (isComponentRoot) {
    List<Integer> component = new ArrayList<>();
    while (true) {
      int k = stack.remove(stack.size() - 1);
      component.add(k);
      lowlink[k] = Integer.MAX_VALUE;
      if (k == u)
        break;
    }
    components.add(component);
  }
}

List<List<Integer>> components = new SCCTarjan().scc(predecessors);