Design-2 Completed

HashMap.java

@@ -0,0 +1,85 @@
+//Approach
+//TC: O(1)
+//SC: O(n)
+
+
+class MyHashMap {
+    Node[] storage;
+    int buckets;
+
+    class Node {
+        int key;
+        int value;
+        Node next;
+
+        public Node(int key, int value) {
+            this.key = key;
+            this.value = value;
+        }
+    }
+
+    public MyHashMap() {
+        this.buckets = 1000;
+        this.storage = new Node[buckets];
+    }
+
+    public int getHash(int key) {
+        return key % buckets;
+    }
+
+    public Node getPrev(Node head, int key) {
+        Node prev = null;
+        Node curr = head;
+        while (curr != null && curr.key != key) {
+            prev = curr;
+            curr = curr.next;
+        }
+        return prev;
+    }
+
+    public void put(int key, int value) {
+        int primary = getHash(key);
+        if (storage[primary] == null) {
+            storage[primary] = new Node(-1, -1);
+            storage[primary].next = new Node(key, value);
+            return;
+        }
+        Node prev = getPrev(storage[primary], key);
+        if (prev.next == null) {
+            prev.next = new Node(key, value);
+        } else {
+            prev.next.value = value;
+        }
+    }
+
+    public int get(int key) {
+        int hash = getHash(key);
+        if (storage[hash] == null)
+            return -1;
+        Node prev = getPrev(storage[hash], key);
+        if (prev.next == null) {
+            return -1;
+        }
+        return prev.next.value;
+    }
+
+    public void remove(int key) {
+        int hash = getHash(key);
+        if (storage[hash] == null) {
+            return;
+        }
+        Node prev = getPrev(storage[hash], 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);
+ */

QueueImpleWithStack.java

@@ -0,0 +1,50 @@
+import java.util.*;
+
+// Approach: 
+// TC:O(1), worstcase - O(n)
+// SC:O(n)
+class MyQueue {
+
+    Stack<Integer> inSt;
+    Stack<Integer> outSt;
+
+    public MyQueue() {
+        this.inSt = new Stack<>();
+        this.outSt = new Stack<>();
+    }
+
+    public void push(int x) {
+        inSt.push(x);
+    }
+
+    public int pop() {
+        if (outSt.isEmpty()) {
+            while (!inSt.isEmpty()) {
+                outSt.push(inSt.pop());
+            }
+        }
+        return outSt.pop();
+    }
+
+    public int peek() {
+        if (outSt.isEmpty()) {
+            while (!inSt.isEmpty()) {
+                outSt.push(inSt.pop());
+            }
+        }
+        return outSt.peek();
+    }
+
+    public boolean empty() {
+        return inSt.isEmpty() && outSt.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();
+ */