design task 2

MyHashMap.java

@@ -0,0 +1,87 @@
+
+public class MyHashMap {
+
+	private int length=1000000;
+    //1-Create ListNode
+    //2-Hash Function
+    //3- find element
+    //4 - implement get
+    // 5 - implement put
+    // 6 - implement remove
+    ListNode[] map=null;
+    class ListNode{
+        int key,val;
+        ListNode next;
+        ListNode(int key, int val){
+            this.key=key;
+            this.val=val;
+        }
+    }
+    public MyHashMap() {
+        map = new ListNode[length];
+    }
+
+    private int hashCode(int key){
+        return Integer.hashCode(key) %  map.length;
+    }
+
+    private ListNode findElement(int index, int key){
+        if (map[index]==null){
+            map[index] =new ListNode(-1,-1);//dummy node
+            return map[index];
+        }else{
+            ListNode currentNode=map[index];
+            while ( currentNode.next!=null && currentNode.next.key!=key){
+                currentNode=currentNode.next;
+            }
+            return currentNode;
+        }
+
+    }
+
+    /*
+     * Average: O(1)
+     * Worst-case: O(N)
+     */
+    public void put(int key, int value) {
+        if (key<0)
+         return ;
+        int hash = hashCode(key);
+        ListNode prevElement=findElement(hash,key);
+        if (prevElement.next!=null){
+            prevElement.next.val=value;
+        }else{
+            prevElement.next= new ListNode(key,value);
+        }
+    }
+
+    /*
+     * Average: O(1)
+     * Worst-case: O(N)
+     */
+    public int get(int key) {
+        if (key<0) return -1;
+        int hash= hashCode(key);
+        ListNode prevElement=findElement(hash,key);
+        if (prevElement.next!=null){
+            return prevElement.next.val;
+        }
+        return -1;
+    }
+
+    /*
+     * Average: O(1)
+     * Worst-case: O(N)
+     */
+    public void remove(int key) {
+        if (key<0)    
+          return;
+        int hashCode = hashCode(key);
+        ListNode prevElement=findElement(hashCode,key);
+        if (prevElement.next ==null ){
+            return;
+        } else{
+            prevElement.next=prevElement.next.next;
+        }
+    }
+}

MyQueue.java

@@ -0,0 +1,40 @@
+import java.util.Stack;
+
+public class MyQueue {
+	Stack<Integer> pushQ, popQ;
+
+	public MyQueue() {
+		pushQ=new Stack<>();
+		popQ= new Stack<>();
+	}
+
+	// time complexity O(1)
+	public void push(int x) {
+		pushQ.push(x);
+	}
+
+	// time complexity O(1) amortized
+	public int peek() {
+	   migrateToPopQueue();
+	   return popQ.peek();
+	}
+
+	// time complexity O(1) amortized
+	public int pop() {
+		migrateToPopQueue();
+		return popQ.pop();		
+	}
+
+	// time complexity O(1)
+	public boolean isEmpty() {
+		return pushQ.isEmpty() && popQ.isEmpty();
+	}
+
+	private void migrateToPopQueue() {
+		if (popQ.isEmpty()) {
+			   while (!pushQ.isEmpty()) {
+				   popQ.push(pushQ.pop());
+			   }
+		}
+	}
+}