问题
I've been able to cook up a Radix tree example in JavaScript (not optimised, so don't judge)
So far I have been able to Add, Transverse and Find nodes.
I'm having trouble writing a function that can retrieve all nodes, this is where I require assistance.Thank you in advance
// As illustrated in:
// http://programminggeeks.com/c-code-for-radix-tree-or-trie/
// Make a class of the Tree so that you can define methods all nodes of the tree
// which are actually Trees in structure inherit the functions
function Tree() {
this.character = undefined;
// if this node is the end of a complete word
// this was we can differentiate "sell" and "sells" if both are searched for
this.isword = false;
// How to nest the nodes, thus creating a tree structure
this.node = {}; // [new Tree(), new Tree(), new Tree()];
// abcdefghijklmnopqrstuvwxyz
var start = 97,
end = start + 25;
function constructor(that) {
for (var x = start; x <= end; x++) {
// for now they are all unsigned objects
that.node[x] = null // new Tree()
}
return that;
}
constructor(this);
return this;
}
Tree.prototype.addNode = function(word) {
return this.transverseNodes(word, true);
};
Tree.prototype.searchForNodes = function(word) {
return this.transverseNodes(word, false);
};
Tree.prototype.stringToNodes = function(word) {
var nodeArray = []
for (var x = 0, length = word.length; x < length; x++) {
nodeArray.push(word.charCodeAt(x));
}
return nodeArray;
};
Tree.prototype.transverseNodes = function(word, bool) {
// make all of the letters lowercase to create uniformity
var nodes = this.stringToNodes(word.toLowerCase());
// console.log(nodes);
// start with parent/root tree
var currentTreeNode = this
// transverse checking if node has been added, if not add it
// if it was already added and it terminates a word set it "isword" property to true
for (var i = 0, length = nodes.length; i < length; i++) {
var node = nodes[i];
// If the current tree node is defined so not overwrite it
if (currentTreeNode.node[node] === null) {
if (!bool) {
// if bool is undefined of false, then this is a search
return false;
}
// create a node
currentTreeNode.node[node] = new Tree();
currentTreeNode.node[node].character = String.fromCharCode(node);
}
// check if the node is the last character of the word
if ((nodes.length - 1) === i) {
// console.log(nodes.length - 1, i)
if (!bool) {
// if bool is undefined of false, then this is a search
return true;
}
currentTreeNode.node[node].isword = true;
}
// get into the nested node
currentTreeNode = currentTreeNode.node[node];
};
return this;
};
var tree = new Tree()
// Create the nodes
tree.addNode("cat");
tree.addNode("camel");
tree.addNode("condom");
tree.addNode("catastrophe");
tree.addNode("grandma");
tree.addNode("lamboghini");
// Search the nodes
console.log(tree.searchForNodes("cat")); // true
console.log(tree.searchForNodes("catapult")); // false
console.log(tree.searchForNodes("catastrophe")); // true
console.log(tree.searchForNodes("mama")); // false
console.log(tree.searchForNodes("lamboghini")); // true
// retrieving all node
// console.log(tree.retrieveAllNodes());
回答1:
This proposal features an iterative and recursive approach for getting the words in the tree.
'use strict';
// As illustrated in:
// http://programminggeeks.com/c-code-for-radix-tree-or-trie/
// Make a class of the Tree so that you can define methods all nodes of the tree
// which are actually Trees in structure inherit the functions
function Tree() {
this.character = undefined;
// if this node is the end of a complete word
// this was we can differentiate "sell" and "sells" if both are searched for
this.isword = false;
// How to nest the nodes, thus creating a tree structure
this.node = {}; // [new Tree(), new Tree(), new Tree()];
// abcdefghijklmnopqrstuvwxyz
var start = 97,
end = start + 25;
function constructor(that) {
for (var x = start; x <= end; x++) {
// for now they are all unsigned objects
that.node[x] = null // new Tree()
}
return that;
}
constructor(this);
return this;
}
Tree.prototype.addNode = function (word) {
return this.transverseNodes(word, true);
};
Tree.prototype.searchForNodes = function (word) {
return this.transverseNodes(word, false);
};
Tree.prototype.stringToNodes = function (word) {
var nodeArray = []
for (var x = 0, length = word.length; x < length; x++) {
nodeArray.push(word.charCodeAt(x));
}
return nodeArray;
};
Tree.prototype.transverseNodes = function (word, bool) {
// make all of the letters lowercase to create uniformity
var nodes = this.stringToNodes(word.toLowerCase());
// console.log(nodes);
// start with parent/root tree
var currentTreeNode = this
// transverse checking if node has been added, if not add it
// if it was already added and it terminates a word set it "isword" property to true
for (var i = 0, length = nodes.length; i < length; i++) {
var node = nodes[i];
// If the current tree node is defined so not overwrite it
if (currentTreeNode.node[node] === null) {
if (!bool) {
// if bool is undefined of false, then this is a search
return false;
}
// create a node
currentTreeNode.node[node] = new Tree();
currentTreeNode.node[node].character = String.fromCharCode(node);
}
// check if the node is the last character of the word
if ((nodes.length - 1) === i) {
// console.log(nodes.length - 1, i)
if (!bool) {
// if bool is undefined of false, then this is a search
return true;
}
currentTreeNode.node[node].isword = true;
}
// get into the nested node
currentTreeNode = currentTreeNode.node[node];
};
return this;
};
Tree.prototype.retrieveAllNodes = function () {
// function for traversing over object, takes the object and an empty string for
// the appearing words, acts as closure for the object
function iterObject(o, r) {
// how i like to start functions with return (...)
// returns basically the up coming word.
// reason for reduce, this provides a return value, with the letters
// of the path
return Object.keys(o).reduce(function (r, key) {
// check if the key property has a truthy value (remember the default
// null values)
if (o[key]) {
// if so, check the property isword
if (o[key].isword) {
// if its truty here, we have a hit, a word is found
wordList.push(r + o[key].character);
};
// check for children
if (o[key].node) {
// if node exist, go on with a new iteration and a new word
// extension
iterObject(o[key].node, r + o[key].character);
}
}
// return the inevitable word stem
return r;
}, r);
}
var wordList = [];
iterObject(this.node, '');
return wordList;
}
var tree = new Tree();
// Create the nodes
tree.addNode("cat");
tree.addNode("camel");
tree.addNode("condom");
tree.addNode("catastrophe");
tree.addNode("grandma");
tree.addNode("lamboghini");
// Search the nodes
console.log(tree.searchForNodes("cat")); // true
console.log(tree.searchForNodes("catapult")); // false
console.log(tree.searchForNodes("catastrophe")); // true
console.log(tree.searchForNodes("mama")); // false
console.log(tree.searchForNodes("lamboghini")); // true
// retrieving all words
console.log(JSON.stringify(tree.retrieveAllNodes(), 0, 4));
// retrieving whole tree
console.log(JSON.stringify(tree, 0, 4));.as-console-wrapper { max-height: 100% !important; top: 0; }Bonus: Below is a version with very small overhead.
'use strict';
function Tree() {
return this;
}
Tree.prototype.addNode = function (word) {
this.stringToNodes(word).reduce(function (node, character, i, a) {
if (!node[character]) {
node[character] = {};
}
if (i === a.length - 1) {
node[character].isword = true;
}
return node[character];
}, this);
return this;
};
Tree.prototype.searchForNodes = function (word) {
function iterObject(o, r) {
return Object.keys(o).reduce(function (r, key) {
if (key === 'isword' && r === word) {
found = true;
}
typeof o[key] === 'object' && iterObject(o[key], r + key);
return r;
}, r);
}
var found = false;
iterObject(this, '');
return found;
};
Tree.prototype.stringToNodes = function (word) {
return word.toLowerCase().split('');
};
Tree.prototype.retrieveAllNodes = function () {
function iterObject(o, r) {
return Object.keys(o).reduce(function (r, key) {
key === 'isword' && wordList.push(r);
typeof o[key] === 'object' && iterObject(o[key], r + key);
return r;
}, r);
}
var wordList = [];
iterObject(this, '');
return wordList;
}
var tree = new Tree();
// Create the nodes
tree.addNode("cat");
tree.addNode("camel");
tree.addNode("condom");
tree.addNode("catastrophe");
tree.addNode("grandma");
tree.addNode("lamboghini");
// Search the nodes
console.log(tree.searchForNodes("cat")); // true
console.log(tree.searchForNodes("catapult")); // false
console.log(tree.searchForNodes("catastrophe")); // true
console.log(tree.searchForNodes("mama")); // false
console.log(tree.searchForNodes("lamboghini")); // true
// retrieving all words
console.log(JSON.stringify(tree.retrieveAllNodes(), 0, 4));
// retrieving whole tree
console.log(JSON.stringify(tree, 0, 4));.as-console-wrapper { max-height: 100% !important; top: 0; }回答2:
I'm not sure if you're doing that for studying, but if not, I suggest you to not reinvent the wheel, and try some library that already exists for that purpose, e.g. Javid Jamae's RadixTreeJS.
来源：https://stackoverflow.com/questions/32595151/how-to-retrieve-all-the-data-words-in-a-radix-trie-in-javascript