August 2 - Design HashSEt

Author: suriyakrishna

src/main/scala/com/leetcode/scala/monthly2020/august/DesignHashSet.scala

@@ -0,0 +1,71 @@
+package com.leetcode.scala.monthly2020.august
+
+/*
+* Design a HashSet without using any built-in hash table libraries.
+* To be specific, your design should include these functions:
+  * add(value): Insert a value into the HashSet.
+  * contains(value) : Return whether the value exists in the HashSet or not.
+  * remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.
+* */
+
+/*
+* MyHashSet hashSet = new MyHashSet();
+  hashSet.add(1);
+  hashSet.add(2);
+  hashSet.contains(1);    // returns true
+  hashSet.contains(3);    // returns false (not found)
+  hashSet.add(2);
+  hashSet.contains(2);    // returns true
+  hashSet.remove(2);
+  hashSet.contains(2);    // returns false (already removed)
+*
+* Note:
+  * All values will be in the range of [0, 1000000].
+  * The number of operations will be in the range of [1, 10000].
+  * Please do not use the built-in HashSet library.
+*
+* */
+
+/*
+* Approach: Using Big Array
+* 1. Since we know the range we can build array of boolean with the range and key will be the index of the array.
+* 2. But lot of space will be wasted.
+* */
+
+class MyHashSet() {
+
+  /** Initialize your data structure here. */
+  private var array: Array[Boolean] = Array.fill(1000001)(false)
+
+  def add(key: Int): Unit = {
+    array(key) = true
+  }
+
+  def remove(key: Int): Unit = {
+    if (array(key)) {
+      array(key) = false
+    }
+  }
+
+  /** Returns true if this set contains the specified element */
+  def contains(key: Int): Boolean = {
+    return array(key)
+  }
+
+}
+
+object DesignHashSet {
+
+  def main(args: Array[String]): Unit = {
+    val hashSet: MyHashSet = new MyHashSet()
+    hashSet.add(1)
+    hashSet.add(2)
+    hashSet.contains(1) // returns true
+    hashSet.contains(3) // returns false (not found)
+    hashSet.add(2)
+    hashSet.contains(2) // returns true
+    hashSet.remove(2)
+    hashSet.contains(2) // returns false (already removed)
+  }
+
+}