/**
* @license
* Copyright The Closure Library Authors.
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @fileoverview Datastructure: Trie.
*
*
* This file provides the implementation of a trie data structure. A trie is a
* data structure that stores key/value pairs in a prefix tree. See:
* http://en.wikipedia.org/wiki/Trie
*/
goog.provide('goog.structs.Trie');
goog.require('goog.object');
goog.require('goog.structs');
/**
* Class for a Trie datastructure. Trie data structures are made out of trees
* of Trie classes.
*
* @param {goog.structs.Trie<VALUE>|Object<string, VALUE>=} opt_trie Optional
* goog.structs.Trie or Object to initialize trie with.
* @constructor
* @template VALUE
*/
goog.structs.Trie = function(opt_trie) {
'use strict';
/**
* This trie's value. For the base trie, this will be the value of the
* empty key, if defined.
* @private {VALUE}
*/
this.value_ = undefined;
/**
* This trie's child nodes.
* @private {!Object<!goog.structs.Trie<VALUE>>}
*/
this.childNodes_ = {};
if (opt_trie) {
this.setAll(opt_trie);
}
};
/**
* Sets the given key/value pair in the trie. O(L), where L is the length
* of the key.
* @param {string} key The key.
* @param {VALUE} value The value.
*/
goog.structs.Trie.prototype.set = function(key, value) {
'use strict';
this.setOrAdd_(key, value, false);
};
/**
* Adds the given key/value pair in the trie. Throw an exception if the key
* already exists in the trie. O(L), where L is the length of the key.
* @param {string} key The key.
* @param {VALUE} value The value.
*/
goog.structs.Trie.prototype.add = function(key, value) {
'use strict';
this.setOrAdd_(key, value, true);
};
/**
* Helper function for set and add. Adds the given key/value pair to
* the trie, or, if the key already exists, sets the value of the key. If
* opt_add is true, then throws an exception if the key already has a value in
* the trie. O(L), where L is the length of the key.
* @param {string} key The key.
* @param {VALUE} value The value.
* @param {boolean=} opt_add Throw exception if key is already in the trie.
* @private
*/
goog.structs.Trie.prototype.setOrAdd_ = function(key, value, opt_add) {
'use strict';
var node = this;
for (var characterPosition = 0; characterPosition < key.length;
characterPosition++) {
var currentCharacter = key.charAt(characterPosition);
if (!node.childNodes_[currentCharacter]) {
node.childNodes_[currentCharacter] = new goog.structs.Trie();
}
node = node.childNodes_[currentCharacter];
}
if (opt_add && node.value_ !== undefined) {
throw new Error('The collection already contains the key "' + key + '"');
} else {
node.value_ = value;
}
};
/**
* Adds multiple key/value pairs from another goog.structs.Trie or Object.
* O(N) where N is the number of nodes in the trie.
* @param {!Object<string, VALUE>|!goog.structs.Trie<VALUE>} trie Object
* containing the data to add.
*/
goog.structs.Trie.prototype.setAll = function(trie) {
'use strict';
var keys = goog.structs.getKeys(trie);
var values = goog.structs.getValues(trie);
for (var i = 0; i < keys.length; i++) {
this.set(keys[i], values[i]);
}
};
/**
* Traverse along the given path, returns the child node at ending.
* Returns undefined if node for the path doesn't exist.
* @param {string} path The path to traverse.
* @return {!goog.structs.Trie<VALUE>|undefined}
* @private
*/
goog.structs.Trie.prototype.getChildNode_ = function(path) {
'use strict';
var node = this;
for (var characterPosition = 0; characterPosition < path.length;
characterPosition++) {
var currentCharacter = path.charAt(characterPosition);
node = node.childNodes_[currentCharacter];
if (!node) {
return undefined;
}
}
return node;
};
/**
* Retrieves a value from the trie given a key. O(L), where L is the length of
* the key.
* @param {string} key The key to retrieve from the trie.
* @return {VALUE|undefined} The value of the key in the trie, or undefined if
* the trie does not contain this key.
*/
goog.structs.Trie.prototype.get = function(key) {
'use strict';
var node = this.getChildNode_(key);
return node ? node.value_ : undefined;
};
/**
* Retrieves all values from the trie that correspond to prefixes of the given
* input key. O(L), where L is the length of the key.
*
* @param {string} key The key to use for lookup. The given key as well as all
* prefixes of the key are retrieved.
* @param {?number=} opt_keyStartIndex Optional position in key to start lookup
* from. Defaults to 0 if not specified.
* @return {!Object<VALUE>} Map of end index of matching prefixes and
* corresponding values. Empty if no match found. Note that the key is the
* index of the final character of the entry, rather than the length, so
* entries with a single character will clobber an empty-string entry with
* key '0'.
*/
goog.structs.Trie.prototype.getKeyAndPrefixes = function(
key, opt_keyStartIndex) {
'use strict';
/** @type {!goog.structs.Trie<VALUE>} */
var node = this;
var matches = {};
var characterPosition = opt_keyStartIndex || 0;
if (node.value_ !== undefined) {
matches[characterPosition] = node.value_;
}
for (; characterPosition < key.length; characterPosition++) {
var currentCharacter = key.charAt(characterPosition);
if (!(currentCharacter in node.childNodes_)) {
break;
}
node = node.childNodes_[currentCharacter];
if (/** @type {VALUE} */ (node.value_) !== undefined) {
matches[characterPosition] = node.value_;
}
}
return matches;
};
/**
* Gets the values of the trie. Not returned in any reliable order. O(N) where
* N is the number of nodes in the trie. Calls getValuesInternal_.
* @return {!Array<VALUE>} The values in the trie.
*/
goog.structs.Trie.prototype.getValues = function() {
'use strict';
var allValues = [];
this.getValuesInternal_(allValues);
return allValues;
};
/**
* Gets the values of the trie. Not returned in any reliable order. O(N) where
* N is the number of nodes in the trie. Builds the values as it goes.
* @param {!Array<VALUE>} allValues Array to place values into.
* @private
*/
goog.structs.Trie.prototype.getValuesInternal_ = function(allValues) {
'use strict';
if (this.value_ !== undefined) {
allValues.push(this.value_);
}
for (var childNode in this.childNodes_) {
this.childNodes_[childNode].getValuesInternal_(allValues);
}
};
/**
* Gets the keys of the trie. Not returned in any reliable order. O(N) where
* N is the number of nodes in the trie (or prefix subtree).
* @param {string=} opt_prefix Find only keys with this optional prefix.
* @return {!Array<string>} The keys in the trie.
*/
goog.structs.Trie.prototype.getKeys = function(opt_prefix) {
'use strict';
var allKeys = [];
if (opt_prefix) {
// Traverse to the given prefix, then call getKeysInternal_ to dump the
// keys below that point.
var node = this;
for (var characterPosition = 0; characterPosition < opt_prefix.length;
characterPosition++) {
var currentCharacter = opt_prefix.charAt(characterPosition);
if (!node.childNodes_[currentCharacter]) {
return [];
}
node = node.childNodes_[currentCharacter];
}
node.getKeysInternal_(opt_prefix, allKeys);
} else {
this.getKeysInternal_('', allKeys);
}
return allKeys;
};
/**
* Private method to get keys from the trie. Builds the keys as it goes.
* @param {string} keySoFar The partial key (prefix) traversed so far.
* @param {!Array<string>} allKeys The partially built array of keys seen so
* far.
* @private
*/
goog.structs.Trie.prototype.getKeysInternal_ = function(keySoFar, allKeys) {
'use strict';
if (this.value_ !== undefined) {
allKeys.push(keySoFar);
}
for (var childNode in this.childNodes_) {
this.childNodes_[childNode].getKeysInternal_(keySoFar + childNode, allKeys);
}
};
/**
* Checks to see if a certain key is in the trie. O(L), where L is the length
* of the key.
* @param {string} key A key that may be in the trie.
* @return {boolean} Whether the trie contains key.
*/
goog.structs.Trie.prototype.containsKey = function(key) {
'use strict';
return this.get(key) !== undefined;
};
/**
* Checks to see if a certain prefix is in the trie. O(L), where L is the length
* of the prefix.
* @param {string} prefix A prefix that may be in the trie.
* @return {boolean} Whether any key of the trie has the prefix.
*/
goog.structs.Trie.prototype.containsPrefix = function(prefix) {
'use strict';
// Empty string is any key's prefix.
if (prefix.length == 0) {
return !this.isEmpty();
}
return !!this.getChildNode_(prefix);
};
/**
* Checks to see if a certain value is in the trie. Worst case is O(N) where
* N is the number of nodes in the trie.
* @param {VALUE} value A value that may be in the trie.
* @return {boolean} Whether the trie contains the value.
*/
goog.structs.Trie.prototype.containsValue = function(value) {
'use strict';
if (this.value_ === value) {
return true;
}
for (var childNode in this.childNodes_) {
if (this.childNodes_[childNode].containsValue(value)) {
return true;
}
}
return false;
};
/**
* Completely empties a trie of all keys and values. ~O(1)
*/
goog.structs.Trie.prototype.clear = function() {
'use strict';
this.childNodes_ = {};
this.value_ = undefined;
};
/**
* Removes a key from the trie or throws an exception if the key is not in the
* trie. O(L), where L is the length of the key.
* @param {string} key A key that should be removed from the trie.
* @return {VALUE} The value whose key was removed.
*/
goog.structs.Trie.prototype.remove = function(key) {
'use strict';
var node = this;
var parents = [];
for (var characterPosition = 0; characterPosition < key.length;
characterPosition++) {
var currentCharacter = key.charAt(characterPosition);
if (!node.childNodes_[currentCharacter]) {
throw new Error('The collection does not have the key "' + key + '"');
}
// Archive the current parent and child name (key in childNodes_) so that
// we may remove the following node and its parents if they are empty.
parents.push([node, currentCharacter]);
node = node.childNodes_[currentCharacter];
}
var oldValue = node.value_;
delete node.value_;
while (parents.length > 0) {
var currentParentAndCharacter = parents.pop();
var currentParent = currentParentAndCharacter[0];
var currentCharacter = currentParentAndCharacter[1];
if (currentParent.childNodes_[currentCharacter].isEmpty()) {
// If the child is empty, then remove it.
delete currentParent.childNodes_[currentCharacter];
} else {
// No point of traversing back any further, since we can't remove this
// path.
break;
}
}
return oldValue;
};
/**
* Clones a trie and returns a new trie. O(N), where N is the number of nodes
* in the trie.
* @return {!goog.structs.Trie<VALUE>} A new goog.structs.Trie with the same
* key value pairs.
*/
goog.structs.Trie.prototype.clone = function() {
'use strict';
return new goog.structs.Trie(this);
};
/**
* Returns the number of key value pairs in the trie. O(N), where N is the
* number of nodes in the trie.
* TODO: This could be optimized by storing a weight (count below) in every
* node.
* @return {number} The number of pairs.
*/
goog.structs.Trie.prototype.getCount = function() {
'use strict';
return goog.structs.getCount(this.getValues());
};
/**
* Returns true if this trie contains no elements. ~O(1).
* @return {boolean} True iff this trie contains no elements.
*/
goog.structs.Trie.prototype.isEmpty = function() {
'use strict';
return this.value_ === undefined && goog.object.isEmpty(this.childNodes_);
};
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