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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,138 @@ | ||
| /* Trie.js | ||
| * written by Colin Kuebler 2012 | ||
| * Part of The Koala Project, licensed under GPLv3 | ||
| * Implements a trie for efficient word completions and corrections | ||
| */ | ||
|
|
||
| function Trie( words ){ | ||
| /* INTERNAL REPRESENTATION */ | ||
| var self = this, | ||
| root = {}, | ||
| size = 0; | ||
| /* INTERNAL METHODS */ | ||
| // traverses the trie to the specified prefix | ||
| function _get( prefix ){ | ||
| var node = root; | ||
| for( var i = 0; i < prefix.length; i++ ){ | ||
| node = node[ prefix.charAt(i) ]; | ||
| if( !node ) return; | ||
| } | ||
| return node; | ||
| }; | ||
| // recursively determines necessary suffix | ||
| function _next( node ){ | ||
| var path, count = 0; | ||
| for( path in node ) if( count++ ) return ''; | ||
| if( node.leaf ) return ' '; | ||
| return path + _next( node[path] ); | ||
| }; | ||
| // recursively determines possible suffixes | ||
| function _list( node ){ | ||
| var results = []; | ||
| for( var i in node ){ | ||
| var suffix = _list( node[i] ); | ||
| for( var j = 0; j < suffix.length; j++ ){ | ||
| results.push( i + suffix[j] ); | ||
| } | ||
| } | ||
| if( node.leaf ) results.push(''); | ||
| return results; | ||
| }; | ||
| // recursively determines words within an edit distance | ||
| function _edits( node, input, allowance ){ | ||
| // shortcuts to the first, second, and remainder of input | ||
| var a = input.charAt(0), b = input.charAt(1), c = input.substr(1); | ||
| // iterator variable and result data structure | ||
| var i, results = {}; | ||
| // merges results together, preserves the lowest cost on conflict | ||
| function merge( prefix, obj, cost ){ | ||
| for( var i in obj ){ | ||
| var key = prefix + i, value = obj[i] + cost; | ||
| results[key] = key in results ? | ||
| Math.min( value, results[key] ) : value; | ||
| } | ||
| }; | ||
| // node is a result iff it is a leaf and there is no more input | ||
| if( node.leaf && !a ) results[''] = 0; | ||
| // MATCH: consume the current letter | ||
| if( node[a] ) merge( a, _edits( node[a], c, allowance ), 0 ); | ||
| // attempt to undo possible edits iff we are within the edit allowance | ||
| if( allowance-- > 0 ){ | ||
| // if there is no next character, only possible edit is deletion | ||
| if( a ){ | ||
| // ADDITION: ignore current letter and continue | ||
| merge( '', _edits( node, c, allowance ), 1 ); | ||
| for( i in node ){ | ||
| // skip match, this is not an edit | ||
| if( a === i ) continue; | ||
| // DELETION: assume correct letter and continue | ||
| merge( i, _edits( node[i], input, allowance ), 1 ); | ||
| // SUBSTITION: assume correct letter, ignore current | ||
| merge( i, _edits( node[i], c, allowance ), 1 ); | ||
| } | ||
| // TRANSPOSITION: swap first and second letter | ||
| if( node[b] && a !== b ) | ||
| merge( b, _edits( node[b], a+c.substr(1), allowance ), 1 ); | ||
| } else { | ||
| // DELETION: assume correct letter | ||
| for( i in node ) | ||
| merge( i, _edits( node[i], '', allowance ), 1 ); | ||
| } | ||
| } | ||
| return results; | ||
| }; | ||
| /* MODIFIERS */ | ||
| self.add = function( word ){ | ||
| var node = root; | ||
| for( var i = 0; i < word.length; i++ ) | ||
| node = node[ word.charAt(i) ] = node[ word.charAt(i) ] || {}; | ||
| if( node.leaf ) return true; | ||
| node.leaf = true; | ||
| size++; | ||
| }; | ||
| self.remove = function( word ){ | ||
| var node = root, | ||
| nodes = [], | ||
| last = word.length; | ||
| for( var i = 0; i < word.length; i++ ){ | ||
| nodes.push( node ); | ||
| node = node[ word.charAt(i) ]; | ||
| if( !node ) return true; | ||
| } | ||
| if( !node.leaf ) return true; | ||
| delete node.leaf; | ||
| size--; | ||
| while( nodes.length ){ | ||
| for( var i in node ) return; | ||
| node = nodes.pop(); | ||
| delete node[ word[--last] ]; | ||
| } | ||
| }; | ||
| /* ACCESSORS */ | ||
| self.all = function(){ | ||
| return _list(root); | ||
| }; | ||
| self.size = function(){ | ||
| return size; | ||
| }; | ||
| /* COOL SHIT */ | ||
| self.next = function( prefix ){ | ||
| var node = _get(prefix); | ||
| return node && _next(node); | ||
| }; | ||
| self.completions = function( prefix ){ | ||
| var node = _get(prefix); | ||
| return node && _list(node); | ||
| }; | ||
| self.check = function( word ){ | ||
| var node = _get(word); | ||
| return node && node.leaf; | ||
| }; | ||
| self.corrections = function( word, distance ){ | ||
| return _edits( root, word, distance ); | ||
| }; | ||
| /* INIT */ | ||
| for( var i = 0; i < words.length; i++ ) self.add( words[i] ); | ||
| return self; | ||
| }; | ||
|
|
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