INTRODUCTION TO TRIE - PART 2
Implementation
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public class Trie {
Node root;
class Node{
boolean isEnd;
Map<Character, Node> hm;
Node(Map<Character, Node> hm){
this.hm = hm;
}
}
public Trie() {
root = new Node(new HashMap<>());
}
public void insert(String word) {
int n = word.length();
Node temp = root;
//Loop through the string
for(int i=0; i<n; i++){
//Get the current character
Character c = Character.valueOf(word.charAt(i));
//Check if the current Node's hashmap contains that character
if(temp.hm.containsKey(c)){
//If it contains the character already, go to the next Node.
//We need to go to the corresponding Node for the current character which we can get from the HashMap.
temp = temp.hm.get(c);
}else{
//If the character is not present in the HashMap, new a new Node which will act like the next one for the current character.
temp.hm.put(c, new Node(new HashMap<>()));
//Once that's is set, go to the next node
temp = temp.hm.get(c);
}
}
temp.isEnd = true;
}
public boolean search(String word) {
int n = word.length();
Node temp = root;
//Loop through the word
for(int i=0; i<n; i++){
//Get the current character
Character c = Character.valueOf(word.charAt(i));
if(!temp.hm.containsKey(c)){
return false;
}else{
temp = temp.hm.get(c);
}
}
//Since we need a complete match and not just prefix, we need to check if isEnd on the current node is true.
return temp.isEnd;
}
public boolean startsWith(String prefix) {
int n = prefix.length();
Node temp = root;
for(int i=0; i<n; i++){
Character c = Character.valueOf(prefix.charAt(i));
if(!temp.hm.containsKey(c)){
return false;
}else{
temp = temp.hm.get(c);
}
}
return true;
}
}