For example we have an array of words:
[car, done, try, cat, trie, do]
What is the best data structure to store the data and easy for search?
We can use Trie data structure, it is a tree, but not a binary tree. The reuslts of constructing a tree by using the example array data.
True of False means whether this letter is the last of the word.
We can code it by Javascript:
- We are using Map data structure
- If there is no existing node for giving letter, we create a new Node.
- If there is a existing node, then we continue to next letter
function Node() {
return {
keys: new Map(),
isWord: false
};
}
function BuildTrie() {
const root = new Node();
return {
root,
add(word, node = this.root) {
if (word.length === 0) {
node.isWord = true;
return;
}
const [head, ...rest] = word;
if (!node.keys.has(head)) {
node.keys.set(head, new Node());
}
return this.add(rest, node.keys.get(head));
},
hasWord(word, node = this.root) {
if (!word) {
return false;
}
while (word.length > 1) {
if (!node.keys.has(word[0])) {
return false;
} else {
node = node.keys.get(word[0]);
word = word.substr(1);
}
}
return node.keys.has(word) && node.keys.get(word).isWord;
},
print() {
let words = [];
function search(node = this.root, string = "") {
if (node.keys.size != 0) {
for (let letter of node.keys.keys()) {
search(node.keys.get(letter), string.concat(letter));
}
if (node.isWord) {
words.push(string);
}
} else {
string.length > 0 ? words.push(string) : undefined;
}
}
search(this.root, "");
return words.length > 0 ? words : null;
}
};
}
const t = new BuildTrie();
t.add("cat");
t.add("cal");
console.log(t.hasWord("cat")); // true
console.log(t.hasWord("catt")); // false