diff --git a/DesignHashMap.java b/DesignHashMap.java
new file mode 100644
index 00000000..f8960a9f
--- /dev/null
+++ b/DesignHashMap.java
@@ -0,0 +1,103 @@
+class MyHashMap {
+
+    class Node {
+        int key;
+        int value;
+        Node next;
+
+        Node(int key, int value) {
+            this.key = key;
+            this.value = value;
+            this.next = null;
+        }
+    }
+
+    private Node[] storage;
+
+
+    public MyHashMap() {
+        this.storage = new Node[10000];
+    }
+
+    private int hash(int key) {
+        return key % 10000;
+    }
+
+
+    private Node find(Node head, int key) {
+
+        Node curr = head;
+        Node prev = null;
+
+        while(curr != null && curr.key != key) {
+            prev = curr;
+            curr = curr.next;
+        }
+        return prev;
+    }
+    
+    public void put(int key, int value) {
+        
+        int idx = hash(key); 
+
+        if (storage[idx] == null) {
+            // initialzie with dummy node
+            storage[idx] = new Node(-1,-1); // dummy
+        }
+
+        Node prev = find(storage[idx], key);
+
+        if(prev.next != null) {
+            prev.next.value = value;
+        }
+        else {
+            Node newNode = new Node(key,value);
+            prev.next = newNode;
+        }    
+    }
+
+            
+    
+    public int get(int key) {
+        
+        int idx = hash(key);
+
+        if(storage[idx] == null) {
+            return -1;
+        }
+        else {
+            Node prev = find(storage[idx],key);
+            Node curr = prev.next;
+            while (curr != null) {
+                if(curr.key == key) {
+                    return curr.value;
+                }
+                curr = curr.next;
+            }
+            return -1;
+        }
+    }
+    
+    public void remove(int key) {
+        
+        int idx = hash(key);
+        if(storage[idx] == null) {
+            return ;
+        }
+        Node prev = find(storage[idx], key);
+
+       if(prev.next == null) {
+        return ;
+       }
+
+       prev.next = prev.next.next;     
+    }
+}
+
+/**
+ * Your MyHashMap object will be instantiated and called as such:
+ * MyHashMap obj = new MyHashMap();
+ * obj.put(key,value);
+ * int param_2 = obj.get(key);
+ * obj.remove(key);
+ */
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diff --git a/QueueUsingStacks.java b/QueueUsingStacks.java
new file mode 100644
index 00000000..d3ce6418
--- /dev/null
+++ b/QueueUsingStacks.java
@@ -0,0 +1,44 @@
+class MyQueue {
+
+    Stack<Integer> in;
+    Stack<Integer> out;
+
+    public MyQueue() {
+        this.in = new Stack<>();
+        this.out = new Stack<>();
+    }
+    
+    public void push(int x) {
+        in.push(x);
+    }
+    
+    public int pop() {
+        
+        peek();
+        return out.pop();
+    }
+    
+    public int peek() {
+        
+        if(out.isEmpty()) {
+
+            while(!in.isEmpty()) {
+                out.push(in.pop());
+            }
+        }
+        return out.peek();
+    }
+    
+    public boolean empty() {
+        return in.isEmpty() && out.isEmpty();
+    }
+}
+
+/**
+ * Your MyQueue object will be instantiated and called as such:
+ * MyQueue obj = new MyQueue();
+ * obj.push(x);
+ * int param_2 = obj.pop();
+ * int param_3 = obj.peek();
+ * boolean param_4 = obj.empty();
+ */
\ No newline at end of file