reachability_tpl.h

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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
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#pragma once
 
// to ease IDE parser
#include <agrum/base/graphs/algorithms/generic/reachability.h>
 
namespace gum::graph {
 
  template < GUM_DiGraphable G >
  NodeSet ancestors(const G& g, NodeId id) {
    NodeSet res;
    NodeSet frontier = g.parents(id);
 
    while (!frontier.empty()) {
      const NodeId current = *frontier.begin();
      frontier.erase(current);
      res.insert(current);
      for (const auto p: g.parents(current))
        if (!res.contains(p)) frontier.insert(p);
    }
 
    return res;
  }
 
  template < GUM_DiGraphable G >
  NodeSet descendants(const G& g, NodeId id) {
    NodeSet res;
    NodeSet frontier = g.children(id);
 
    while (!frontier.empty()) {
      const NodeId current = *frontier.begin();
      frontier.erase(current);
      res.insert(current);
      for (const auto c: g.children(current))
        if (!res.contains(c)) frontier.insert(c);
    }
 
    return res;
  }
 
  template < GUM_DiGraphable G >
  NodeSet family(const G& g, NodeId id) {
    NodeSet res{id};
    return res + g.parents(id);
  }
 
  template < GUM_DiGraphable G >
  NodeSet family(const G& g, const NodeSet& ids) {
    NodeSet res;
    for (const auto node: ids)
      res += family(g, node);
    return res;
  }
 
  template < GUM_UndiGraphable G >
  NodeProperty< NodeId > chainComponents(const G& g) {
    NodeProperty< NodeId > res;
    NodeId                 numCC = 0;
 
    for (const auto node: g.nodes()) {
      if (res.exists(node)) continue;
 
      NodeSet frontier{node};
      while (!frontier.empty()) {
        const NodeId current = *frontier.begin();
        frontier.erase(current);
        res.insert(current, numCC);
        for (const auto nei: g.neighbours(current))
          if (!res.exists(nei)) frontier.insert(nei);
      }
      ++numCC;
    }
 
    return res;
  }
 
  template < GUM_NodeGraphable G >
  NodeProperty< NodeId > connectedComponents(const G& g) {
    NodeProperty< NodeId > res;
    NodeId                 numCC = 0;
 
    for (const auto node: g.nodes()) {
      if (res.exists(node)) continue;
 
      NodeSet frontier{node};
      while (!frontier.empty()) {
        const NodeId current = *frontier.begin();
        frontier.erase(current);
        res.insert(current, numCC);
 
        if constexpr (GUM_DiGraphable< G >) {
          for (const auto n: g.parents(current))
            if (!res.exists(n)) frontier.insert(n);
          for (const auto n: g.children(current))
            if (!res.exists(n)) frontier.insert(n);
        }
        if constexpr (GUM_UndiGraphable< G >) {
          for (const auto n: g.neighbours(current))
            if (!res.exists(n)) frontier.insert(n);
        }
      }
      ++numCC;
    }
 
    return res;
  }
 
  template < GUM_UndiGraphable G >
  bool areConnected(const G& g, const NodeSet& A, const NodeSet& B) {
    if (A.empty() || B.empty()) return false;
    if (!(A * B).empty()) return true;
 
    NodeSet visited;
    NodeSet frontier = A;
    for (const auto s: A)
      visited.insert(s);
 
    while (!frontier.empty()) {
      const NodeId u = *frontier.begin();
      frontier.erase(u);
      for (const auto v: g.neighbours(u)) {
        if (visited.exists(v)) continue;
        if (B.contains(v)) return true;
        visited.insert(v);
        frontier.insert(v);
      }
    }
    return false;
  }
 
  template < GUM_MixedGraphable G >
  NodeSet chainComponent(const G& g, NodeId node) {
    NodeSet res;
    NodeSet frontier{node};
 
    while (!frontier.empty()) {
      const NodeId n = *frontier.begin();
      frontier.erase(n);
      res.insert(n);
      for (const auto nei: g.neighbours(n))
        if (!res.contains(nei)) frontier.insert(nei);
    }
 
    return res;
  }
 
  template < GUM_MixedGraphable G >
  NodeSet boundary(const G& g, NodeId node) {
    return g.neighbours(node) + g.parents(node) + g.children(node);
  }
 
}   // namespace gum::graph