diff --git a/155. Min Stack/MinStack.java b/155. Min Stack/MinStack.java
new file mode 100644
index 00000000..85e71169
--- /dev/null
+++ b/155. Min Stack/MinStack.java	
@@ -0,0 +1,53 @@
+class MinStack {
+
+    private Stack<Integer> st;
+    private Stack<Integer> minst;
+    private int min;
+
+    public MinStack() {
+
+        this.st = new Stack<>();
+        this.minst = new Stack<>();
+        this.min = Integer.MAX_VALUE;
+        minst.push(min); // setting minStack value to infinity
+    }
+    
+    public void push(int val) {
+
+        if(val < min){
+            min = val;
+        }
+
+        st.push(val);
+        minst.push(min);
+        
+    }
+    
+    public void pop() {
+        st.pop();
+        minst.pop();
+        min = minst.peek(); // set min value to minst top value i.e. the min value
+    }
+    
+    public int top() {
+
+        return st.peek();
+        
+    }
+    
+    public int getMin() {
+        return min;
+    }
+}
+
+// TC - O(1)
+// SC - O(n)
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * MinStack obj = new MinStack();
+ * obj.push(val);
+ * obj.pop();
+ * int param_3 = obj.top();
+ * int param_4 = obj.getMin();
+ */
\ No newline at end of file
diff --git a/705. Design HashSet/MyHashSet.java b/705. Design HashSet/MyHashSet.java
new file mode 100644
index 00000000..8757427b
--- /dev/null
+++ b/705. Design HashSet/MyHashSet.java	
@@ -0,0 +1,81 @@
+class MyHashSet {
+
+    int primaryBucket;
+    int secondaryBucket;
+    boolean[][] storage;
+
+    public MyHashSet() {
+
+        this.primaryBucket = 1000;
+        this.secondaryBucket = 1000;
+        this.storage = new boolean[primaryBucket][];
+
+    }
+
+    public int primaryKey(int key) {
+
+        return key % primaryBucket;
+
+    }
+
+    public int secondaryKey(int key) {
+
+        return key / secondaryBucket;
+
+    }
+
+    public void add(int key) {
+
+        int primaryIndex = primaryKey(key);
+
+        if (storage[primaryIndex] == null) {
+
+            if (primaryIndex == 0) {
+                storage[primaryIndex] = new boolean[secondaryBucket + 1];
+            } else {
+                storage[primaryIndex] = new boolean[secondaryBucket];
+            }
+
+        }
+
+        int secondaryIndex = secondaryKey(key);
+        storage[primaryIndex][secondaryIndex] = true;
+
+    }
+
+    public void remove(int key) {
+
+        int primaryIndex = primaryKey(key);
+
+        if(storage[primaryIndex] == null){
+
+            return;
+        }
+
+        int secondaryIndex = secondaryKey(key); 
+        storage[primaryIndex][secondaryIndex] = false;
+
+    }
+
+    public boolean contains(int key) {
+
+        int primaryIndex = primaryKey(key);
+
+        if (storage[primaryIndex] == null) {
+
+            return false;
+        }
+        int secondaryIndex = secondaryKey(key);
+
+        return storage[primaryIndex][secondaryIndex];
+
+    }
+}
+
+/**
+ * Your MyHashSet object will be instantiated and called as such:
+ * MyHashSet obj = new MyHashSet();
+ * obj.add(key);
+ * obj.remove(key);
+ * boolean param_3 = obj.contains(key);
+ */
\ No newline at end of file