go: add «1268. Search Suggestions System»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/search-suggestions-system.go

@@ -0,0 +1,80 @@
+package search_suggestions_system
+
+type TrieNode struct {
+	has        bool
+	successors [26]*TrieNode
+}
+
+type Trie struct {
+	root TrieNode
+}
+
+func Constructor() Trie {
+	return Trie{}
+}
+
+func (this *Trie) Insert(word string) {
+	node := &this.root
+
+	for _, c := range word {
+		idx := int(c) - int('a')
+
+		if node.successors[idx] == nil {
+			node.successors[idx] = new(TrieNode)
+		}
+		node = node.successors[idx]
+	}
+
+	node.has = true
+}
+
+func (this *Trie) Suggest(word string) [][]string {
+	firstThree := func(node *TrieNode, prefix string) []string {
+		words := make([]string, 0, 3)
+
+		var dfs func(*TrieNode, string)
+		dfs = func(node *TrieNode, prefix string) {
+			if len(words) == 3 || node == nil {
+				return
+			}
+
+			if node.has {
+				words = append(words, prefix)
+			}
+
+			for i, child := range node.successors {
+				if child == nil {
+					continue
+				}
+
+				dfs(child, prefix+string(rune(i+int('a'))))
+			}
+		}
+
+		dfs(node, prefix)
+		return words
+	}
+
+	suggestions := make([][]string, len(word))
+	node := &this.root
+
+	for i, c := range word {
+		idx := int(c) - int('a')
+		if node != nil {
+			node = node.successors[idx]
+		}
+
+		suggestions[i] = firstThree(node, word[:i+1])
+	}
+
+	return suggestions
+}
+
+func suggestedProducts(products []string, searchWord string) [][]string {
+	trie := Constructor()
+	for _, product := range products {
+		trie.Insert(product)
+	}
+
+	return trie.Suggest(searchWord)
+}