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#pragma once
#include "base/macros.hpp"
#include "base/stl_add.hpp"
#include <algorithm>
#include <cstdint>
#include <map>
#include <memory>
#include <vector>
namespace my
{
// This class is a simple in-memory trie which allows to add
// key-value pairs and then traverse them in a sorted order.
template <typename String, typename Value>
class MemTrie
{
private:
struct Node;
public:
using Char = typename String::value_type;
MemTrie() = default;
MemTrie(MemTrie && rhs) { *this = std::move(rhs); }
MemTrie & operator=(MemTrie && rhs)
{
m_root = std::move(rhs.m_root);
m_numNodes = rhs.m_numNodes;
rhs.Clear();
return *this;
}
// A read-only iterator wrapping a Node. Any modification to the
// underlying trie is assumed to invalidate the iterator.
class Iterator
{
public:
Iterator(MemTrie::Node const & node) : m_node(node) {}
// Iterates over all possible moves from this Iterator's node
// and calls |toDo| with two arguments:
// (Char of the move, Iterator wrapping the node of the move).
template <typename ToDo>
void ForEachMove(ToDo && toDo) const
{
for (auto const & move : m_node.m_moves)
toDo(move.first, Iterator(*move.second));
}
// Calls |toDo| for every value in this Iterator's node.
template <typename ToDo>
void ForEachInNode(ToDo && toDo) const
{
std::for_each(m_node.m_values.begin(), m_node.m_values.end(), std::forward<ToDo>(toDo));
}
private:
MemTrie::Node const & m_node;
};
// Adds a key-value pair to the trie.
void Add(String const & key, Value const & value)
{
auto * cur = &m_root;
for (auto const & c : key)
{
bool created;
cur = &cur->GetMove(c, created);
if (created)
++m_numNodes;
}
cur->AddValue(value);
}
// Traverses all key-value pairs in the trie and calls |toDo| on each of them.
template <typename ToDo>
void ForEachInTrie(ToDo && toDo) const
{
String prefix;
ForEachInSubtree(m_root, prefix, std::forward<ToDo>(toDo));
}
// Calls |toDo| for each key-value pair in the node that is reachable
// by |prefix| from the trie root. Does nothing if such node does
// not exist.
template <typename ToDo>
void ForEachInNode(String const & prefix, ToDo && toDo) const
{
if (auto const * root = MoveTo(prefix))
ForEachInNode(*root, prefix, std::forward<ToDo>(toDo));
}
// Calls |toDo| for each key-value pair in a subtree that is
// reachable by |prefix| from the trie root. Does nothing if such
// subtree does not exist.
template <typename ToDo>
void ForEachInSubtree(String prefix, ToDo && toDo) const
{
if (auto const * root = MoveTo(prefix))
ForEachInSubtree(*root, prefix, std::forward<ToDo>(toDo));
}
void Clear()
{
m_root.Clear();
m_numNodes = 1;
}
size_t GetNumNodes() const { return m_numNodes; }
Iterator GetRootIterator() const { return Iterator(m_root); }
Node const & GetRoot() const { return m_root; }
private:
struct Node
{
friend class MemTrie<String, Value>::Iterator;
Node() = default;
Node(Node && /* rhs */) = default;
Node & operator=(Node && /* rhs */) = default;
Node & GetMove(Char const & c, bool & created)
{
auto & node = m_moves[c];
if (!node)
{
node = my::make_unique<Node>();
created = true;
}
else
{
created = false;
}
return *node;
}
void AddValue(Value const & value) { m_values.push_back(value); }
void Clear()
{
m_moves.clear();
m_values.clear();
}
std::map<Char, std::unique_ptr<Node>> m_moves;
std::vector<Value> m_values;
DISALLOW_COPY(Node);
};
Node const * MoveTo(String const & key) const
{
auto const * cur = &m_root;
for (auto const & c : key)
{
auto const it = cur->m_moves.find(c);
if (it == cur->m_moves.end())
return nullptr;
cur = it->second.get();
}
return cur;
}
// Calls |toDo| for each key-value pair in a |node| that is
// reachable by |prefix| from the trie root.
template <typename ToDo>
void ForEachInNode(Node const & node, String const & prefix, ToDo && toDo) const
{
for (auto const & value : node.m_values)
toDo(prefix, value);
}
// Calls |toDo| for each key-value pair in subtree where |node| is a
// root of the subtree. |prefix| is a path from the trie root to the
// |node|.
template <typename ToDo>
void ForEachInSubtree(Node const & node, String & prefix, ToDo && toDo) const
{
ForEachInNode(node, prefix, toDo);
for (auto const & move : node.m_moves)
{
prefix.push_back(move.first);
ForEachInSubtree(*move.second, prefix, toDo);
prefix.pop_back();
}
}
Node m_root;
size_t m_numNodes = 1;
DISALLOW_COPY(MemTrie);
};
} // namespace my
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