Completed Design 2 problems

MyHashMap_DoubleHashing.java

@@ -0,0 +1,80 @@
+// Using double hashing
+
+// 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
+// I am using double hashing to handle collisions.
+// The hash function is designed to distribute keys evenly across the buckets, reducing the likelihood of collisions.
+// When a collision occurs, the second hash function is used to determine the bucket item index, further reducing the
+// chance of collisions within the same bucket.
+// Also, I am using wrapper class Integer instead of primitive int to handle null values, which is necessary for collision resolution.
+// And returing the -1 if key is not found in get method. As int would have default value of 0.
+
+
+class MyHashMap {
+
+    Integer [][] storage;
+    int buckets;
+    int bucketItems;
+
+    public MyHashMap() {
+        this.buckets = 1000;
+        this.bucketItems = 1000;
+        this.storage = new Integer[buckets][];
+    }
+
+    private int hash1(int key){
+        return key % buckets;
+    }
+    private int hash2(int key){
+        return key / buckets;
+    }
+
+    // Time Complexity : O(1)
+    // Space Complexity : O(1)
+    public void put(int key, int value) {
+        int bucket = hash1(key);
+        int bucketItem = hash2(key);
+
+        if(storage[bucket] == null){
+            if(bucket == 0){
+                storage[bucket] = new Integer[bucketItems + 1];
+            }else{
+                storage[bucket] = new Integer[bucketItems];
+            }
+
+        }
+        storage[bucket][bucketItem] = value;
+    }
+
+    // Time Complexity : O(1)
+    // Space Complexity : O(1)
+    public int get(int key) {
+        int bucket = hash1(key);
+        int bucketItem = hash2(key);
+
+        if(storage[bucket] == null || storage[bucket][bucketItem] == null) return -1;
+        return storage[bucket][bucketItem];
+    }
+
+    // Time Complexity : O(1)
+    // Space Complexity : O(1)
+    public void remove(int key) {
+        int bucket = hash1(key);
+        int bucketItem = hash2(key);
+
+        if(storage[bucket] == null || storage[bucket][bucketItem] == null) return;
+        storage[bucket][bucketItem] = null;
+    }
+}
+
+/**
+ * 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);
+ */

MyHashMap_chaining.java

@@ -0,0 +1,102 @@
+// 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
+// I am using the chaining approach to implement the hashmap. The basic idea is to use an array of linked lists to store key-value pairs.
+// The hash function is used to determine the index in the array where the key-value pair should be stored.
+// When a collision occurs, the key-value pair is added to the linked list at that index.
+// The search operation involves traversing the linked list at the index to find the key-value pair.
+// The put operation involves adding a new key-value pair to the linked list at the index, or updating the value if the key already exists.
+// The get operation involves searching the linked list at the index for the key and returning the corresponding value.
+// The remove operation involves searching the linked list at the index for the key and removing the key-value pair if found.
+
+class MyHashMap {
+    private class Node{
+        int key, value;
+        Node next;
+        Node(int key, int value){
+            this.key = key;
+            this.value = value;
+        }
+    }
+    private Node [] storage;
+    private int buckets;
+    public MyHashMap() {
+        this.buckets = 10000;
+        this.storage =  new Node[buckets];
+    }
+
+    // Time Complexity : O(1)
+    // Space Complexity : O(1)
+    private int myHashFunction (int key){
+        return key % buckets;
+    }
+
+    // Time Complexity : amortized O(1)
+    // Space Complexity : O(1)
+    private Node search(Node head , int key){
+
+        Node previousNode = head;
+        Node currentNode = previousNode.next;
+
+        while(currentNode != null && currentNode.key != key){
+            previousNode = currentNode;
+            currentNode = currentNode.next;
+        }
+        return previousNode;
+
+    }
+
+    // Time Complexity : amortized O(1)
+    // Space Complexity : O(1)
+
+    public void put(int key, int value) {
+        int index = myHashFunction(key);
+        if(storage[index] == null){
+            storage[index] = new Node(-1,-1);
+        }
+        Node prev = search(storage[index], key);
+        if(prev.next == null){
+            prev.next = new Node(key, value);
+        }else{
+            prev.next.value = value;
+        }
+    }
+
+    // Time Complexity : amortized O(1)
+    // Space Complexity : O(1)
+
+    public int get(int key) {
+        int index = myHashFunction(key);
+        if(storage[index] == null) return -1;
+
+        Node prev = search(storage[index], key);
+
+        if(prev.next == null || prev.next.key != key) return -1;
+        return prev.next.value;
+
+    }
+
+    // Time Complexity : amortized O(1)
+    // Space Complexity : O(1)
+
+    public void remove(int key) {
+        int index = myHashFunction(key);
+        if(storage[index] == null) return;
+        Node prev = search(storage[index], 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);
+ */

QueueUsingStacks.java

@@ -0,0 +1,65 @@
+
+// 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
+// The MyQueue class implements a queue using two stacks. The inStack is used for enqueue operations, 
+// while the outStack is used for dequeue and peek operations. When the outStack is empty, 
+// elements are transferred from inStack to outStack to maintain the queue order.
+
+class MyQueue {
+    Stack<Integer> inStack;
+    Stack<Integer> outStack;
+
+    public MyQueue() {
+        this.inStack = new Stack<>();
+        this.outStack = new Stack<>();
+    }
+
+    /**
+     * Time Complexity: O(1)
+     * Space Complexity: O(1)
+     */
+    public void push(int x) {
+        inStack.push(x);
+    }
+
+    /**
+     * Time Complexity: Amortized O(1), Worst case O(n)
+     * Space Complexity: O(1)
+     */
+    public int pop() {
+        peek();
+        return outStack.pop();
+    }
+
+    /**
+     * Time Complexity: Amortized O(1), Worst case O(n)
+     * Space Complexity: O(1)
+     */
+    public int peek() {
+        if(outStack.isEmpty()){
+            while(!inStack.isEmpty()){
+                outStack.push(inStack.pop());
+            }
+        }
+        return outStack.peek();
+    }
+
+    /**
+     * Time Complexity: O(1)
+     * Space Complexity: O(1)
+     */
+    public boolean empty() {
+        return inStack.isEmpty() && outStack.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();
+ */