Removed usage of prefix in a node, just a key is enough

Author: santhoshvai

Trie/Trie.ts

@@ -1,26 +1,24 @@
+// represents the leaf node's key from its parent, meaning thats the end of a word
+const LEAF_NODE_NOTATION = "$"
+
 class Node {
   edges: Map<string, Node> = new Map()
-  prefix: string
   isWordEnd: boolean = false
 
-  constructor(prefix = "") {
-    this.prefix = prefix
-  }
-
   // adds the char to the edge if not present, and returns the edge
   // or returns the edge if already present
   addChar = (char: string): Node => {
     if (this.edges.has(char)) {
       return this.edges.get(char)!
     }
-    const node = new Node(this.prefix + char)
+    const node = new Node()
     this.edges.set(char, node)
     return node
   }
 
   addLeaf = (): Node => {
-    const node = new Node(this.prefix)
-    this.edges.set(this.prefix, node)
+    const node = new Node()
+    this.edges.set(LEAF_NODE_NOTATION, node)
     node.isWordEnd = true
     return node
   }
@@ -67,49 +65,52 @@ export default class Trie {
   }
 
   // walk the trie until we find the last matching char
-  _walkTrieForBestMatch = (word: string): { node: Node, length: number } => {
+  _walkTrieForBestMatch = (word: string): { node: Node, length: number, stringMatched: string } => {
     let currentNode: Node = this._head
+    let stringMatched = ""
     let i = 0;
     for (;i < word.length; i++) {
       const char = word.charAt(i)
       const node = currentNode.getEdge(char)
       if (node === undefined) break;
       else {
+        stringMatched = stringMatched + char
         currentNode = node
       }
     }
     // the head node has a empty char, so the length will be equal to index that we have walked so far
-    return { node: currentNode, length: i }
+    return { node: currentNode, length: i, stringMatched }
   }
 
-  // send empty word to accept partial matches
-  _walkNodeToGetWords = (node: Node, patterns: Set<string>, word = "") => {
+  // send empty word to accept partial matches, parent is used for recursion
+  _walkNodeToGetWords = (node: Node, patterns: Set<string>, word = "", parent = "") => {
     if (node.isWordEnd) {
       // the if check is to avoid partial matches
-      // for example, when we check for "partyy" we should not return "part"
-      if (word.length <= node.prefix.length) {
-        patterns.add(node.prefix)
+      // for example, when we check for "partyy" we should not return "part" or "party"
+      if (word.length <= parent.length) {
+        patterns.add(parent)
       }
       return
     }
     for (const [key, value] of node.edges) {
       // the next constructed words' predecessor must have have the last predecssor + current key
       // like "lo" + "r" then onto "lor" then "e" and "m"
-      this._walkNodeToGetWords(value, patterns, word) 
+      const nextParent = key === LEAF_NODE_NOTATION ? parent : (parent + key) // when key is "$", dont add it to parent string
+      this._walkNodeToGetWords(value, patterns, word, nextParent) 
     }
   }
 
   hasWord = (word: string): boolean => {
     const { node, length } = this._walkTrieForBestMatch(word)
-    const endNode = node.getEdge(word)
+    const endNode = node.getEdge(LEAF_NODE_NOTATION)
     const hasEndNode = endNode !== undefined && endNode.isWordEnd
     return (length === word.length && hasEndNode)
   }
 
   getSuggestions = (word: string, acceptPartialMatch = false): Set<string> => {
-    const { node } = this._walkTrieForBestMatch(word)
+    const { node, stringMatched } = this._walkTrieForBestMatch(word)
     const patterns: Set<string> = new Set()
-    this._walkNodeToGetWords(node, patterns, acceptPartialMatch ? "" : word)
+    this._walkNodeToGetWords(node, patterns, acceptPartialMatch ? "" : word, stringMatched)
     return patterns
   }