trie_policy_base.hpp
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// -*- C++ -*-
// Copyright (C) 2005-2026 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the terms
// of the GNU General Public License as published by the Free Software
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// version.
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// General Public License for more details.
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// 3.1, as published by the Free Software Foundation.
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// a copy of the GCC Runtime Library Exception along with this program;
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// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
// Permission to use, copy, modify, sell, and distribute this software
// is hereby granted without fee, provided that the above copyright
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/**
* @file trie_policy/trie_policy_base.hpp
* Contains an implementation of trie_policy_base.
*/
#ifndef PB_DS_TRIE_POLICY_BASE_HPP
#define PB_DS_TRIE_POLICY_BASE_HPP
#include <ext/pb_ds/detail/branch_policy/branch_policy.hpp>
namespace __gnu_pbds
{
namespace detail
{
/// Base class for trie policies.
template<typename Node_CItr, typename Node_Itr,
typename _ATraits, typename _Alloc>
class trie_policy_base
: public branch_policy<Node_CItr, Node_Itr, _Alloc>
{
typedef branch_policy<Node_CItr, Node_Itr, _Alloc> base_type;
public:
typedef _ATraits access_traits;
typedef _Alloc allocator_type;
typedef typename allocator_type::size_type size_type;
typedef null_type metadata_type;
typedef Node_CItr node_const_iterator;
typedef Node_Itr node_iterator;
typedef typename node_const_iterator::value_type const_iterator;
typedef typename node_iterator::value_type iterator;
typedef typename base_type::key_type key_type;
typedef typename base_type::key_const_reference key_const_reference;
protected:
virtual const_iterator
end() const = 0;
virtual iterator
end() = 0;
virtual node_const_iterator
node_begin() const = 0;
virtual node_iterator
node_begin() = 0;
virtual node_const_iterator
node_end() const = 0;
virtual node_iterator
node_end() = 0;
virtual const access_traits&
get_access_traits() const = 0;
private:
typedef typename access_traits::const_iterator e_const_iterator;
typedef std::pair<e_const_iterator, e_const_iterator> prefix_range_t;
protected:
static size_type
common_prefix_len(node_iterator, e_const_iterator,
e_const_iterator, const access_traits&);
static iterator
leftmost_it(node_iterator);
static iterator
rightmost_it(node_iterator);
static bool
less(e_const_iterator, e_const_iterator, e_const_iterator,
e_const_iterator, const access_traits&);
};
#define PB_DS_CLASS_T_DEC \
template<typename Node_CItr, typename Node_Itr, \
typename _ATraits, typename _Alloc>
#define PB_DS_CLASS_C_DEC \
trie_policy_base<Node_CItr, Node_Itr, _ATraits, _Alloc>
PB_DS_CLASS_T_DEC
typename PB_DS_CLASS_C_DEC::size_type
PB_DS_CLASS_C_DEC::
common_prefix_len(node_iterator nd_it, e_const_iterator b_r,
e_const_iterator e_r, const access_traits& r_traits)
{
prefix_range_t pref_range = nd_it.valid_prefix();
e_const_iterator b_l = pref_range.first;
e_const_iterator e_l = pref_range.second;
const size_type range_length_l = std::distance(b_l, e_l);
const size_type range_length_r = std::distance(b_r, e_r);
if (range_length_r < range_length_l)
{
std::swap(b_l, b_r);
std::swap(e_l, e_r);
}
size_type ret = 0;
while (b_l != e_l)
{
if (r_traits.e_pos(*b_l) != r_traits.e_pos(*b_r))
return ret;
++ret;
++b_l;
++b_r;
}
return ret;
}
PB_DS_CLASS_T_DEC
typename PB_DS_CLASS_C_DEC::iterator
PB_DS_CLASS_C_DEC::
leftmost_it(node_iterator nd_it)
{
if (nd_it.num_children() == 0)
return *nd_it;
return leftmost_it(nd_it.get_child(0));
}
PB_DS_CLASS_T_DEC
typename PB_DS_CLASS_C_DEC::iterator
PB_DS_CLASS_C_DEC::
rightmost_it(node_iterator nd_it)
{
const size_type num_children = nd_it.num_children();
if (num_children == 0)
return *nd_it;
return rightmost_it(nd_it.get_child(num_children - 1));
}
PB_DS_CLASS_T_DEC
bool
PB_DS_CLASS_C_DEC::
less(e_const_iterator b_l, e_const_iterator e_l,
e_const_iterator b_r, e_const_iterator e_r,
const access_traits& r_traits)
{
while (b_l != e_l)
{
if (b_r == e_r)
return false;
size_type l_pos = r_traits.e_pos(*b_l);
size_type r_pos = r_traits.e_pos(*b_r);
if (l_pos != r_pos)
return (l_pos < r_pos);
++b_l;
++b_r;
}
return b_r != e_r;
}
#undef PB_DS_CLASS_T_DEC
#undef PB_DS_CLASS_C_DEC
} // namespace detail
} // namespace __gnu_pbds
#endif // #ifndef PB_DS_TRIE_POLICY_BASE_HPP
branch_policy.hpp
std::distance
constexpr iterator_traits< _InputIterator >::difference_type distance(_InputIterator __first, _InputIterator __last)
A generalization of pointer arithmetic.
Definition stl_iterator_base_funcs.h:172
__gnu_pbds
GNU extensions for policy-based data structures for public use.
Definition assoc_container.hpp:52
std::pair
Struct holding two objects (or references) of arbitrary type.
Definition stl_pair.h:307
__gnu_pbds::null_type
Represents no type, or absence of type, for template tricks.
Definition tag_and_trait.hpp:210
__gnu_pbds::detail::size_type
__gnu_pbds::detail::branch_policy
Primary template, base class for branch structure policies.
Definition branch_policy.hpp:54
__gnu_pbds::detail::trie_policy_base
Base class for trie policies.
Definition trie_policy_base.hpp:55