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Commit 9f7e002

Browse files 
2 parents a47d639 + b169cda commit 9f7e002

16 files changed

+503
-0
lines changed
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package DSA_College.DoublyLinkedList;
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public class DoublyLinkedList {
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ListNode head;
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ListNode tail;
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int size = 0;
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DoublyLinkedList() {
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this.head = null;
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this.tail = null;
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this.size = 0;
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}
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// ListNode class
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private static class ListNode {
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int data;
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ListNode prev;
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ListNode next;
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ListNode(int data) {
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this.data = data;
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this.prev = null;
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this.next = null;
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}
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}
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// add node at start
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public void insertFirst(int data) {
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ListNode node = new ListNode(data);
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if (head == null) {
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head = node;
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node.next = null;
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tail = node;
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} else {
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node.next = head;
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node.prev = null;
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head = node;
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}
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size ++;
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}
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// insert at index
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public void insert(int index, int data) {
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ListNode node = new ListNode(data);
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if (head == null) {
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insertFirst(data);
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} else {
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ListNode n = head;
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int i = 0;
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while (i < index - 1) {
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n = n.next;
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i ++;
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}
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node.next = n.next;
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n.next.prev = node;
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n.next = node;
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node.prev = n;
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}
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size ++;
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}
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// insert at last
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public void insertLast(int data) {
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ListNode node = new ListNode(data);
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if (head == null) {
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insertFirst(data);
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} else {
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node.prev = tail;
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tail.next = node;
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node.next = null;
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tail = node;
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size++;
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}
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}
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// returns size of the linked list
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public int size() {
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return size;
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}
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// method to check is linked list empty or not
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public boolean isEmpty() {
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return size == 0;
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}
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// display forward
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public void displayForward() {
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ListNode n = head;
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while (n != null) {
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System.out.print(n.data + " -> ");
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n = n.next;
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}
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System.out.println("null");
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}
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// display backward
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public void displayBackward() {
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ListNode n = tail;
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while (n != null) {
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System.out.print(n.data + " -> ");
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n = n.prev;
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}
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System.out.println("null");
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}
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// delete at first
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public int deleteFirst() {
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if (isEmpty()) {
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System.out.println("List is Empty");
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return -1;
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}
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if (head == tail) {
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int data = head.data;
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head = tail = null;
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return data;
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}
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int data = head.data;
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head = head.next;
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head.prev = null;
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return data;
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}
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// delete last
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public int deleteLast() {
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if (isEmpty()) {
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System.out.println("List is Empty");
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return -1;
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}
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if (head == tail) {
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int data = head.data;
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head = tail = null;
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return data;
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}
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int data = tail.data;
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tail = tail.next;
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tail.prev = null;
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return data;
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}
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public static void main(String[] args) {
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DoublyLinkedList dll = new DoublyLinkedList();
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dll.insertFirst(10);
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dll.insertFirst(20);
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dll.insertFirst(30);
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dll.displayForward();
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System.out.println(dll.size());
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dll.insertLast(5);
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dll.displayForward();
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System.out.println(dll.size());
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dll.insert(2, 25);
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dll.displayForward();
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System.out.println(dll.size());
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dll.displayBackward();
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System.out.println();
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dll.displayForward();
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System.out.println("Deleted Node => " + dll.deleteFirst());
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dll.displayForward();
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System.out.println(dll.size());
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}
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}

‎Leetcode/Leetcode_101.java

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‎Leetcode/Leetcode_1071.java

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package Leetcode;
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public class Leetcode_1071 {
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public static String gcdOfStrings(String str1, String str2) {
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String r = "";
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int len = Math.min(str1.length(), str2.length());
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for (int i = 0; i < len; i++) {
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if (true)
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return "";
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}
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return r;
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}
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public static void main(String[] args) {
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System.out.println(gcdOfStrings("ABCABC", "ABC"));
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}
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}

‎Leetcode/Leetcode_112.java

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package Leetcode;
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//class Leetcode_112 {
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// public boolean hasPathSum(TreeNode root, int targetSum) {
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// if (root == null)
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// return false;
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// if (root.left == null && root.right == null)
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// return root.val - targetSum == 0;
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// return hasPathSum(root.left, targetSum - root.val) || hasPathSum(root.right, targetSum - root.val);
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// }
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//}

‎Leetcode/Leetcode_155.java

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package Leetcode;
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import java.util.Stack;
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// Leetcode 155
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class MinStack {
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Stack<Integer> s;
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public MinStack() {
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s = new Stack<>();
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}
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public void push(int val) {
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s.push(val);
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}
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public void pop() {
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s.pop();
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}
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public int top() {
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return s.peek();
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}
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public int getMin() {
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Stack<Integer> s2 = new Stack<>();
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int min = Integer.MAX_VALUE;
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while (!s.isEmpty()) {
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int a = s.pop();
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min = Integer.min(a, min);
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s2.push(a);
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}
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while (!s2.isEmpty()) {
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int a = s2.pop();
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s.push(a);
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}
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return min;
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}
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}

‎Leetcode/Leetcode_169.java

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package Leetcode;
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import java.util.HashMap;
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// majority element
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public class Leetcode_169 {
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public static int majorityElement(int[] nums) {
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HashMap<Integer, Integer> h = new HashMap<>();
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for (int num : nums)
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h.put(num, h.getOrDefault(num, 0) + 1);
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for (int num : nums)
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if (h.get(num) > (nums.length / 2))
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return num;
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return -1;
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}
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public static void main(String[] args) {
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System.out.println(majorityElement(new int[]{2,2,1,1,1,2,2}));
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}
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}

‎Leetcode/Leetcode_226.java

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package Leetcode;
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class TreeNode {
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int val;
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TreeNode left;
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TreeNode right;
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TreeNode() {
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}
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TreeNode(int val) {
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this.val = val;
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}
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TreeNode(int val, TreeNode left, TreeNode right) {
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this.val = val;
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this.left = left;
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this.right = right;
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}
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}
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public class Leetcode_226 {
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public TreeNode invertTree(TreeNode root) {
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if (root == null)
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return null;
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TreeNode left = invertTree(root.left);
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TreeNode right = invertTree(root.right);
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// swapping of nodes
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root.right = left;
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root.left = right;
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return root;
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}
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}

‎Leetcode/Leetcode_231.java

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package Leetcode;
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public class Leetcode_231 {
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// iterative approach
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// public boolean isPowerOfTwo(int n) {
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// if (n <= 0)
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// return false;
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// while(n > 1) {
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// if (n % 2 != 0)
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// return false;
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// n = n / 2;
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// }
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// return true;
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// }
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// bitwise approach
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// public static boolean isPowerOfTwo(int n) {
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// int a = Integer.bitCount(n);
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// return a == 1;
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//
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// }
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// bitwise approach 2
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public static boolean isPowerOfTwo(int n) {
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if (n == 0)
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return false;
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return ((long) n & ((long) n - 1)) == 0;
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}
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public static void main(String[] args) {
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System.out.println(isPowerOfTwo(28));
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}
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}

‎Leetcode/Leetcode_240.java

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package Leetcode;
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import java.util.Arrays;
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public class Leetcode_240 {
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public static boolean searchMatrix(int[][] matrix, int target) {
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return searchRow(matrix, target);
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}
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public static boolean searchRow(int[][] m, int target){
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for (int[] ints : m) {
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boolean r = binarySearch(ints, target);
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if (r == true)
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return true;
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}
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return false;
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}
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public static boolean binarySearch(int[] m, int target){
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int r = Arrays.binarySearch(m, target);
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return r >= 0;
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}
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public static void main(String[] args) {
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int target = 5;
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int[][] m = {{1,4,7,11,15},{2,5,8,12,19},{3,6,9,16,22},{10,13,14,17,24},{18,21,23,26,30}};
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System.out.println(searchMatrix(m, target));
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}
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}

‎Leetcode/Leetcode_26.java

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package Leetcode;
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// remove duplicates from a sorted array
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public class Leetcode_26 {
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public static int removeDuplicates(int[] nums) {
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StringBuilder a = new StringBuilder();
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for (int num : nums) {
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if (!a.toString().contains(num + "")) {
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a.append(num);
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}
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}
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for (int i = 0; i < a.length(); i++) {
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nums[i] = Integer.parseInt(a.charAt(i) + "");
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}
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return a.length();
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}
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public static void main(String[] args) {
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System.out.println(removeDuplicates(new int[]{0,0,1,1,1,2,2,3,3,4}));
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}
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}

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