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Commit f739f55

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Merge remote-tracking branch 'origin/master'
2 parents f5c5972 + efc0b39 commit f739f55

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8 files changed

+520
-1
lines changed

8 files changed

+520
-1
lines changed

‎CONTRIBUTING.md

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make a PR

‎DoublyLinkedList/DoublyLinkedList.java

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package DoublyLinkedList;
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public class DoublyLinkedList {
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Node head;
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Node tail;
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int size = 0;
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// add the node at last
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public void add(int data) {
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Node node = new Node(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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node.prev = head;
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} else {
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node.prev = tail;
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tail.next = node;
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}
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tail = node;
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size ++;
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}
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// add node at a index
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public void add (int data, int index) {
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Node node = new Node(data);
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if (index == 0) {
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addFirst(data);
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}
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else if (index == size - 1) {
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add(data);
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}
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else if (index >= size) {
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throw new IndexOutOfBoundsException("Index does not exists");
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}
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else {
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Node crr = head;
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int i = 1;
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while (i < index - 1) {
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// System.out.println(crr.data);
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crr = crr.next;
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i++;
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}
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node.next = crr.next;
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node.prev = crr;
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crr.next = node;
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size++;
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}
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}
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// add the node at first
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public void addFirst(int data) {
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Node node = new Node(data);
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node.next = head;
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head = node;
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node.prev = head;
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size ++;
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}
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// delete a node from last
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public int delete() {
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int data = 0;
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if (head == null)
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throw new IndexOutOfBoundsException("Linked List is Empty!!");
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else {
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data = tail.data;
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tail.prev.next = null;
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tail = tail.next;
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size --;
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}
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return data;
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}
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// delete a node from start
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public int deleteFirst() {
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int data = 0;
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if (head == null)
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throw new ArrayIndexOutOfBoundsException("Linked List is Empty!!");
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else {
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data = head.data;
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head = head.next;
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head.prev = head;
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size --;
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}
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return data;
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}
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// display the list
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public void display() {
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Node 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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// delete a node at any index
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public int delete(int index) {
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int i = 0, data = 0;
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Node crr = head;
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while (i ++ < index - 1) {
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crr = crr.next;
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}
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data = crr.next.data;
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crr.next = crr.next.next;
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crr.next.prev = crr;
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size --;
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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.add(10);
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dll.add(20);
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dll.add(30);
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dll.display();
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dll.addFirst(6);
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dll.display();
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dll.addFirst(5);
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dll.display();
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dll.add(25, 2);
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dll.display();
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System.out.println("Last Deleted Node => " + dll.delete());
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dll.display();
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System.out.println("First Deleted Node => " + dll.deleteFirst());
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dll.display();
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System.out.println("Deleted Node => " + dll.delete(2));
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dll.display();
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}
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}

‎Leetcode/Leetcode_20.java

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package Leetcode;
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import java.util.Stack;
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public class Leetcode_20 {
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public boolean isValid(String s) {
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Stack<Integer> st =new Stack<Integer>();
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char a[]=s.toCharArray();
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int comp=0;
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for(int i=0;i<s.length();i++){
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if(i>0 && !st.isEmpty()){comp=st.peek();}
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st.push((int) a[i]);
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if(comp!=0 && !st.isEmpty() && st.size()>1){
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if((comp==91 && st.peek()==93)||(comp==123 && st.peek()==125)||(comp==40 && st.peek()==41)){
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st.pop();st.pop();}
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}
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}
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return st.isEmpty();
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}
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}

‎Leetcode/Leetcode_203.java

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package Leetcode;
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import DSA_College.LinkList.ListNode;
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import java.util.HashMap;
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public class Leetcode_203 {
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public ListNode removeElements(ListNode head, int val) {
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if(head == null)
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return head;
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ListNode curr = head;
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ListNode pre = null;
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while(curr != null){
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if(curr.data == val && pre!=null){
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pre.next = curr.next;
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curr = curr.next;
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}else if(curr.data == val){
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curr = curr.next;
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head = curr;
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} else{
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pre = curr;
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curr = curr.next;
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}
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}
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return head;
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}
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}

‎Leetcode/Leetcode_225.java

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package Leetcode;
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import java.util.LinkedList;
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import java.util.Queue;
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public class Leetcode_225 {
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Queue<Integer> q1;
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Queue<Integer> q2;
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Leetcode_225() {
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this.q1 = new LinkedList<>();
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this.q2 = new LinkedList<>();
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}
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public void push(int x) {
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q1.add(x);
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while (!q1.isEmpty())
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q2.add(q1.remove());
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while (!q2.isEmpty())
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q1.add(q2.remove());
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}
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public int pop() {
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if (q1.isEmpty())
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return -1;
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while (!q1.isEmpty())
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q2.add(q1.remove());
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int res = q2.remove();
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while (!q2.isEmpty())
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q1.add(q2.remove());
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return res;
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}
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public int top() {
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if (q1.isEmpty())
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return -1;
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while (!q1.isEmpty())
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q2.add(q1.remove());
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int res = q2.peek();
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while (!q2.isEmpty())
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q1.add(q2.remove());
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return res;
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}
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public boolean empty() {
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return q1.isEmpty();
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}
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}

‎Leetcode/Leetcode_232.java

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package Leetcode;
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import java.util.Stack;
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public class Leetcode_232 {
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int peek;
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Stack<Integer> s1;
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Stack<Integer> s2;
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// public Leetcode_232() {
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// this.s1 = new Stack<>();
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// this.s2 = new Stack<>();
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// }
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//
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// public void push(int x) {
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// s1.push(x);
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// }
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//
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// public int pop() {
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// if (empty())
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// return -1;
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// while (!s1.isEmpty()) {
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// s2.push(s1.pop());
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// }
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// peek = s2.peek();
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// int data = s2.pop();
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// while (!s2.isEmpty())
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// s1.push(s2.pop());
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// return data;
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// }
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//
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// public int peek() {
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// if (s1.isEmpty())
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// return -1;
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// return peek;
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// }
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//
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// public boolean empty() {
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// return s1.isEmpty();
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// }
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Leetcode_232() {
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s1 = new Stack<>();
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s2 = new Stack<>();
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}
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public void push(int x) {
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if(empty()) {
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s1.push(x);
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}else {
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while(s1.size()>0) {
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s2.push(s1.pop());
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}
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s1.push(x);
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while(s2.size()>0) {
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s1.push(s2.pop());
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}
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}
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}
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public int pop() {
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if(empty())
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return -1;
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return s1.pop();
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}
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public int peek() {
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if(empty())
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return -1;
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return s1.peek();
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}
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public boolean empty() {
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return s1.isEmpty();
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}
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public static void main(String[] args) {
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Leetcode_232 l = new Leetcode_232();
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l.push(10);
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l.push(20);
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l.push(30);
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l.push(40);
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System.out.println(l.empty());
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System.out.println(l.peek());
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System.out.println(l.pop());
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}
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}

‎MainClass.java

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import java.util.Comparator;
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import java.util.LinkedList;
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import java.util.Scanner;
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// this is the main class.
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public class MainClass {
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public static void main(String[] args) {
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LinkedList <Friend> friends = new LinkedList<>();

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