Custom HashSet done

Author: rampatra

src/main/java/com/leetcode/arrays/RemoveDuplicates.java

@@ -15,14 +15,16 @@
  * <p>
  * Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively.
  * <p>
- * It doesn't matter what you leave beyond the returned length.
+ * NOTE: It doesn't matter what you leave beyond the returned length.
  *
  * @author rampatra
  * @since 2019-04-24
  */
 public class RemoveDuplicates {
 
     /**
+     * This removes the duplicates from the array in-place.
+     * <p>
      * Time complexity: O(n)
      * where,
      * n = no. of elements in the array

src/main/java/com/leetcode/hashtables/ContainsDuplicates.java

@@ -0,0 +1,49 @@
+package com.leetcode.hashtables;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Level: Easy
+ * Problem Link: https://leetcode.com/problems/contains-duplicate/
+ *
+ * @author rampatra
+ * @since 2019-04-24
+ */
+public class ContainsDuplicates {
+
+    public static boolean containsDuplicates(int[] nums) {
+        Set<Integer> numSet = new HashSet<>();
+        for (int num : nums) {
+            if (!numSet.add(num)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Runtime: <a href="https://leetcode.com/submissions/detail/224724092/">5 ms</a>.
+     *
+     * @param nums
+     * @return
+     */
+    public static boolean containsDuplicatesWithoutSet(int[] nums) {
+        Arrays.sort(nums);
+        for (int i = 0; i < nums.length - 1; i++) {
+            if (nums[i] == nums[i + 1]) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(containsDuplicates(new int[]{1, 2, 3, 1}));
+        System.out.println(containsDuplicates(new int[]{1, 2, 3, 4}));
+        
+        System.out.println(containsDuplicatesWithoutSet(new int[]{1, 2, 3, 1}));
+        System.out.println(containsDuplicatesWithoutSet(new int[]{1, 2, 3, 4}));
+    }
+}

src/main/java/com/leetcode/hashtables/MyHashSet.java

@@ -0,0 +1,92 @@
+package com.leetcode.hashtables;
+
+/**
+ * Level: Learning Cards
+ * Problem Link: https://leetcode.com/explore/learn/card/hash-table/182/practical-applications/1139/
+ *
+ * @author rampatra
+ * @since 2019-04-24
+ */
+public class MyHashSet {
+
+    private final int SIZE = 10000;
+    private final Entry[] entries;
+
+    class Entry {
+        int key;
+        Entry next;
+
+        Entry(int key) {
+            this.key = key;
+        }
+    }
+
+    /**
+     * Initialize your data structure here.
+     */
+    public MyHashSet() {
+        entries = new Entry[SIZE];
+    }
+
+    public void add(int key) {
+        if (contains(key)) return;
+        
+        Entry newEntry = new Entry(key);
+        int bucket = key % SIZE;
+
+        newEntry.next = entries[bucket];
+        entries[bucket] = newEntry;
+    }
+
+    public void remove(int key) {
+        int bucket = key % SIZE;
+        Entry entry = entries[bucket];
+        
+        if (entry != null && entry.key == key) {
+            entries[bucket] = entry.next;
+            return;
+        }
+        
+        Entry curr = new Entry(0);
+        curr.next = entry;
+        
+        while (curr.next != null && curr.next.key != key) {
+            curr = curr.next;
+        }
+        
+        if (curr.next != null) {
+            curr.next = curr.next.next;
+        }
+    }
+
+    /**
+     * Returns true if this set contains the specified element
+     */
+    public boolean contains(int key) {
+        int bucket = key % SIZE;
+        Entry entry = entries[bucket];
+
+        while (entry != null) {
+            if (entry.key == key) {
+                return true;
+            }
+            entry = entry.next;
+        }
+
+        return false;
+    }
+
+    public static void main(String[] args) {
+        MyHashSet set = new MyHashSet();
+        set.add(1);
+        set.add(2);
+        set.add(3);
+        System.out.println(set.contains(1));
+        System.out.println(set.contains(2));
+        set.remove(2);
+        System.out.println(set.contains(2));
+        System.out.println(set.contains(3));
+        set.remove(3);
+        System.out.println(set.contains(3));
+    }
+}