Tries, conversions and field goals
Post on 29-Jun-2015
1515 Views
Preview:
DESCRIPTION
Transcript
Tries, Conversions and Field GoalsA RUGBY (LEAGUE) FAN’S GUIDE TO TRIE DATA STRUCTURES
Who am I?Mark Baker
Design and Development ManagerInnovEd (Innovative Solutions for Education) Ltd
Coordinator and Developer of:Open Source PHPOffice library
PHPExcel, PHPWord,PHPPowerPoint, PHPProject, PHPVisioMinor contributor to PHP core
@Mark_Baker
https://github.com/MarkBaker
http://uk.linkedin.com/pub/mark-baker/b/572/171
Tries – What is a Trie? A trie is a key/value data structure that stores the information about the key of each node in the path from the root to the node, rather than in the node itself.
Each path between the root and a leaf represents a key.
Each transition between two nodes is labelled with a single character from a key.
Typically (though not always) the keys will be string values.
Tries – What is a Trie? A special marker on each node indicates whether or not it represents the end of a key.
An “end” node may still have child nodes.
Tries – What is a Trie? Methods:
◦ Insert(key, value)◦ Delete(key)◦ Search(key)
Tries – What is a Trie? Used for:
◦ Dictionary lookups◦ Predictive text / Autocomplete◦ Spell checkers◦ DNA sequencing◦ Burst Sort
Conversions – Tries in PHPclass TrieNode { /** * Array of child nodes indexed by next character * * @var TrieNode[] **/ public $children = array();
/** * Flag indicating if this node is an end node * * @var boolean **/ public $valueNode = false;
/** * Data value (empty unless this is an end node) * * @var mixed **/ public $value; }
Conversions – Tries in PHP
Conversions – Tries in PHP
Conversions – Tries in PHP class Trie {
/** * Adds a new entry to the Trie * If the specified node already exists, then its value will be overwritten * * @param mixed $key Key for this node entry * @param mixed $value Data Value for this node entry * @return null */ public function add($key, $value = null) { $trieNodeEntry = $this->getTrieNodeByKey($key, true); $trieNodeEntry->valueNode = true; $trieNodeEntry->value = $value; }
}
Conversions – Tries in PHP
Conversions – Tries in PHP class Trie {
/** * Backtrack toward the root of the Trie, deleting as we go,
* until we reach a node that we shouldn't delete * * @param TrieNode $trieNode This node entry * @param mixed $key The full key for this node entry * @return null */ private function delete_backtrace(TrieNode $trieNode, $key) { $previousKey = substr($key, 0, -1); $thisChar = substr($key, -1); $previousTrieNode = $this->getTrieNodeByKey($previousKey); unset($previousTrieNode->children[$thisChar]);
if ((count($previousTrieNode->children) == 0) && (!$previousTrieNode->valueNode)) { $this->delete_backtrace($previousTrieNode, $previousKey); } }
/** * Delete a node in the Trie * * @param mixed $key The key for the node that we want to delete * @return boolean Success or failure, false if the node didn't exist */ public function delete($key) { $trieNode = $this->getTrieNodeByKey($key); if (!$trieNode) { return false; }
if (!empty($trieNode->children)) { $trieNode->valueNode = false; $trieNode->value = null; } else { $this->delete_backtrace($trieNode, $key); }
return true; }
}
Conversions – Tries in PHP function buildTries($fileName) { $playerData = json_decode( file_get_contents($fileName) );
$trie = new \Trie(); foreach($playerData as $player) { $playerName = $player->surname . ', ' . $player->firstname; $trie->add($playerName, $player); } return $trie; }
/* Populate the trie */ $tries = buildTries(__DIR__ . '/RugbyData.json');
/* Do some searches */ $searchResult = $tries->search($searchName); if (empty($searchResult)) { echo 'No matches found', PHP_EOL; } else { $players = array_slice($searchResult, 0, $limit); foreach($players as $player) { echo $player->surname, ', ', $player->firstname, PHP_EOL; } }
Conversions – Tries in PHP/usr/mark/presentations/tries php trieSearch.php HallLoad Time: 0.0221 sCurrent Memory: 4499.16 kPeak Memory: 4569.01 k
Hall, BillHall, HarryHall, JamesHall, MartinHalliwell, BillyHalliwell, CHalliwell, FrankHalliwell, Jimmy
Search Time: 0.0045 sCurrent Memory: 4500.70 kPeak Memory: 4569.01 k
Field Goals – Compressed Tries
Field Goals – Patricia TriesPatricia - Practical Algorithm to Retrieve Information Coded in Alphanumeric
Field Goals
Questions?
top related