pathFinding_tpl.h

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 *   This file is part of the aGrUM/pyAgrum library.                        *
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 *   Copyright (c) 2005-2026 by                                             *
 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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 *   SPDX-FileCopyrightText: Copyright 2005-2026                            *
 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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#pragma once
 
#include <agrum/base/graphs/algorithms/generic/pathFinding.h>
 
namespace gum::graph {
 
  namespace detail {
    inline std::vector< NodeId >
        reconstructPath(const NodeProperty< NodeId >& mark, NodeId n1, NodeId n2) {
      std::vector< NodeId > v;
      NodeId                cur = n1;
      while (cur != n2) {
        v.push_back(cur);
        if (!mark.exists(cur))
          GUM_ERROR(NotFound, "reconstructPath: no BFS predecessor for node " << cur)
        cur = mark[cur];
      }
      v.push_back(n2);
      return v;
    }
  }   // namespace detail
 
  template < GUM_DiGraphable G >
  std::optional< std::vector< NodeId > > directedPath(const G& g, NodeId n1, NodeId n2) {
    List< NodeId > fifo;
    fifo.pushBack(n2);
    NodeProperty< NodeId > mark;
    mark.insert(n2, n2);
 
    while (!fifo.empty()) {
      const NodeId current = fifo.front();
      fifo.popFront();
      for (const auto n: g.parents(current)) {
        if (mark.exists(n)) continue;
        mark.insert(n, current);
        if (n == n1) return detail::reconstructPath(mark, n1, n2);
        fifo.pushBack(n);
      }
    }
 
    return std::nullopt;
  }
 
  template < GUM_DiGraphable G >
  std::optional< std::vector< NodeId > > directedUnorientedPath(const G& g, NodeId n1, NodeId n2) {
    List< NodeId > fifo;
    fifo.pushBack(n2);
    NodeProperty< NodeId > mark;
    mark.insert(n2, n2);
 
    auto tryVisit = [&](NodeId n, NodeId from) -> bool {
      if (mark.exists(n)) return false;
      mark.insert(n, from);
      if (n == n1) return true;
      fifo.pushBack(n);
      return false;
    };
 
    while (!fifo.empty()) {
      const NodeId current = fifo.front();
      fifo.popFront();
      for (const auto n: g.parents(current))
        if (tryVisit(n, current)) return detail::reconstructPath(mark, n1, n2);
      for (const auto n: g.children(current))
        if (tryVisit(n, current)) return detail::reconstructPath(mark, n1, n2);
    }
 
    return std::nullopt;
  }
 
  template < GUM_DiGraphable G >
  bool hasDirectedPath(const G& g, NodeId from, NodeId to) {
    if (!g.existsNode(from)) return false;
 
    List< NodeId > fifo;
    fifo.pushBack(from);
    NodeSet marked{from};
 
    while (!fifo.empty()) {
      const NodeId current = fifo.front();
      fifo.popFront();
      for (const auto chi: g.children(current)) {
        if (chi == to) return true;
        if (!marked.contains(chi)) {
          fifo.pushBack(chi);
          marked.insert(chi);
        }
      }
    }
 
    return false;
  }
 
  template < GUM_UndiGraphable G >
  std::optional< std::vector< NodeId > > undirectedPath(const G& g, NodeId n1, NodeId n2) {
    List< NodeId > fifo;
    fifo.pushBack(n2);
    NodeProperty< NodeId > mark;
    mark.insert(n2, n2);
 
    while (!fifo.empty()) {
      const NodeId current = fifo.front();
      fifo.popFront();
      for (const auto n: g.neighbours(current)) {
        if (mark.exists(n)) continue;
        mark.insert(n, current);
        if (n == n1) return detail::reconstructPath(mark, n1, n2);
        fifo.pushBack(n);
      }
    }
 
    return std::nullopt;
  }
 
  template < GUM_UndiGraphable G >
  bool hasUndirectedPath(const G& g, NodeId n1, NodeId n2) {
    NodeSet visited;
    NodeSet frontier{n1};
 
    while (!frontier.empty()) {
      const NodeId current = *frontier.begin();
      if (current == n2) return true;
      frontier.erase(current);
      visited.insert(current);
      for (const auto next: g.neighbours(current))
        if (!visited.contains(next)) frontier.insert(next);
    }
 
    return false;
  }
 
  template < GUM_UndiGraphable G >
  bool hasUndirectedPath(const G& g, NodeId n1, NodeId n2, const NodeSet& except) {
    if (except.contains(n2)) return false;
 
    NodeSet visited;
    NodeSet frontier{n1};
 
    while (!frontier.empty()) {
      const NodeId current = *frontier.begin();
      if (current == n2) return true;
      frontier.erase(current);
      visited.insert(current);
      for (const auto next: g.neighbours(current))
        if (!visited.contains(next) && !except.contains(next)) frontier.insert(next);
    }
 
    return false;
  }
 
  template < GUM_UndiGraphable G >
  bool hasUndirectedPath(const G& g, const NodeSet& n1, const NodeSet& n2, const NodeSet& except) {
    NodeSet visited;
    NodeSet frontier(n1);
 
    while (!frontier.empty()) {
      const NodeId current = *frontier.begin();
      if (n2.contains(current)) return true;
      frontier.erase(current);
      visited.insert(current);
      for (const auto next: g.neighbours(current))
        if (!visited.contains(next) && !except.contains(next)) frontier.insert(next);
    }
 
    return false;
  }
 
  template < GUM_MixedGraphable G >
  std::optional< std::vector< NodeId > > mixedOrientedPath(const G& g, NodeId n1, NodeId n2) {
    List< NodeId > fifo;
    fifo.pushBack(n2);
    NodeProperty< NodeId > mark;
    mark.insert(n2, n2);
 
    auto tryVisit = [&](NodeId n, NodeId from) -> bool {
      if (mark.exists(n)) return false;
      mark.insert(n, from);
      if (n == n1) return true;
      fifo.pushBack(n);
      return false;
    };
 
    while (!fifo.empty()) {
      const NodeId current = fifo.front();
      fifo.popFront();
      for (const auto n: g.neighbours(current))
        if (tryVisit(n, current)) return detail::reconstructPath(mark, n1, n2);
      for (const auto n: g.parents(current))
        if (tryVisit(n, current)) return detail::reconstructPath(mark, n1, n2);
    }
 
    return std::nullopt;
  }
 
  template < GUM_MixedGraphable G >
  bool hasMixedOrientedPath(const G& g, NodeId n1, NodeId n2) {
    return mixedOrientedPath(g, n1, n2).has_value();
  }
 
  template < GUM_MixedGraphable G >
  std::optional< std::vector< NodeId > > mixedUnorientedPath(const G& g, NodeId n1, NodeId n2) {
    List< NodeId > fifo;
    fifo.pushBack(n2);
    NodeProperty< NodeId > mark;
    mark.insert(n2, n2);
 
    auto tryVisit = [&](NodeId n, NodeId from) -> bool {
      if (mark.exists(n)) return false;
      mark.insert(n, from);
      if (n == n1) return true;
      fifo.pushBack(n);
      return false;
    };
 
    while (!fifo.empty()) {
      const NodeId current = fifo.front();
      fifo.popFront();
      for (const auto n: g.neighbours(current))
        if (tryVisit(n, current)) return detail::reconstructPath(mark, n1, n2);
      for (const auto n: g.parents(current))
        if (tryVisit(n, current)) return detail::reconstructPath(mark, n1, n2);
      for (const auto n: g.children(current))
        if (tryVisit(n, current)) return detail::reconstructPath(mark, n1, n2);
    }
 
    return std::nullopt;
  }
 
}   // namespace gum::graph