Completed Design -1 HashSet

Sample.java

@@ -1,7 +1,70 @@
-// Time Complexity :
-// Space Complexity :
-// Did this code successfully run on Leetcode :
-// Any problem you faced while coding this :
+// Time Complexity : O(1)
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
 
 
 // Your code here along with comments explaining your approach
+
+// MyHashSet — a HashSet built from a 2D grid ("hotel with floors and rooms")
+//
+// Big idea: instead of one giant array of a million booleans, we split each
+// key into (floor, room) using % and /, and only build a floor's rooms the
+// first time a key actually lands on that floor.
+
+class MyHashSet {
+
+    let primaryBuckets = 1000
+    let secondaryBuckets = 1000
+
+    var storage: [[Bool]?]
+
+    init() {
+        storage = [[Bool]?](repeating: nil, count: primaryBuckets)
+    }
+
+    private func getPrimaryHash(_ key: Int) -> Int {
+        return key % primaryBuckets
+    }
+
+    private func getSecondaryHash(_ key: Int) -> Int {
+        return key / secondaryBuckets
+    }
+
+    func add(_ key: Int) {
+        let primaryIndex = getPrimaryHash(key)
+
+        if storage[primaryIndex] == nil {
+            if primaryIndex == 0 {
+                storage[primaryIndex] = [Bool](repeating: false, count: secondaryBuckets + 1)
+            } else {
+                storage[primaryIndex] = [Bool](repeating: false, count: secondaryBuckets)
+            }
+        }
+
+        let secondaryIndex = getSecondaryHash(key)
+        storage[primaryIndex]![secondaryIndex] = true
+    }
+
+    func remove(_ key: Int) {
+        let primaryIndex = getPrimaryHash(key)
+
+        guard storage[primaryIndex] != nil else {
+            return
+        }
+
+        let secondaryIndex = getSecondaryHash(key)
+        storage[primaryIndex]![secondaryIndex] = false
+    }
+
+    func contains(_ key: Int) -> Bool {
+        let primaryIndex = getPrimaryHash(key)
+
+        guard storage[primaryIndex] != nil else {
+            return false
+        }
+
+        let secondaryIndex = getSecondaryHash(key)
+        return storage[primaryIndex]![secondaryIndex]
+    }
+}