Add Design A Trie

Author: marttp

kotlin/src/main/kotlin/common/tries/DesignTrie.kt

@@ -0,0 +1,55 @@
+package common.tries
+
+class DesignTrie {
+    class Trie {
+        val root = TrieNode()
+
+        // insert
+        fun insert(word: String) {
+            var node = root
+            for (c in word.toCharArray()) {
+                // For each character in the word, if it's not a child of
+                // the current node, create a new TrieNode for that
+                // character.
+                val index = c - 'a'
+                if (node.children[index] == null) {
+                    node.children[index] = TrieNode()
+                }
+                node = node.children[index]!!
+            }
+            // Mark the last node as the end of a word.
+            node.isWord = true
+        }
+
+        // search
+        fun search(word: String): Boolean {
+            var node = root
+            for (c in word.toCharArray()) {
+                // For each character in the word, if it's not a child of
+                // the current node, the word doesn't exist in the Trie.
+                val index = c - 'a'
+                if (node.children[index] == null) {
+                    return false
+                }
+                node = node.children[index]!!
+            }
+            // Return whether the current node is marked as the end of the word.
+            return node.isWord
+        }
+
+        // hasPrefix
+        fun hasPrefix(word: String): Boolean {
+            var node = root
+            for (c in word.toCharArray()) {
+                val index = c - 'a'
+                if (node.children[index] == null) {
+                    return false
+                }
+                node = node.children[index]!!
+            }
+            // Once we've traversed the nodes corresponding to each
+            // character in the prefix, return True.
+            return true
+        }
+    }
+}

kotlin/src/main/kotlin/common/tries/TrieNode.kt

@@ -0,0 +1,7 @@
+package common.tries
+
+data class TrieNode(
+    var isWord: Boolean = false,
+    var word: String? = null,
+    val children: Array<TrieNode?> = Array(26) { null }
+)

kotlin/src/test/kotlin/common/tries/DesignTrieTest.kt

@@ -0,0 +1,65 @@
+package common.tries
+
+import common.tries.DesignTrie.Trie
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeAll
+import org.junit.jupiter.api.Test
+
+class DesignTrieTest {
+
+    @Test
+    fun `Expected containing word`() {
+        assertTrue { trie.search("banana") }
+        assertTrue { trie.search("pineapple") }
+    }
+
+    @Test
+    fun `Expected not containing word`() {
+        assertFalse { trie.search("kiwi") }
+    }
+
+    @Test
+    fun `Expected contain prefix`() {
+        assertTrue { trie.hasPrefix("water") }
+        assertTrue { trie.hasPrefix("black") }
+    }
+
+    @Test
+    fun `Expected not contain prefix`() {
+        assertFalse { trie.hasPrefix("white") }
+    }
+
+    companion object {
+
+        val fruits: List<String> = listOf(
+            "apple",
+            "banana",
+            "grape",
+            "orange",
+            "watermelon",
+            "strawberry",
+            "blueberry",
+            "mango",
+            "pineapple",
+            "peach",
+            "cherry",
+            "pear",
+            "plum",
+            "blackberry",
+            "raspberry",
+            "coconut",
+            "papaya"
+        )
+
+        private lateinit var trie: Trie
+
+        @JvmStatic
+        @BeforeAll
+        fun init() {
+            trie = Trie()
+            for (fruit in fruits) {
+                trie.insert(fruit)
+            }
+        }
+    }
+}