2B)

import java.util.LinkedList;

import java.util.Queue;

import java.util.Scanner;

class Program2b{

Queue<Integer> q1 = new LinkedList<>();

Queue<Integer> q2 = new LinkedList<>();

public void push(int x) {

q2.add(x);

while (!q1.isEmpty()) {

q2.add(q1.remove());

Queue<Integer> temp = q1;

q1 = q2;

q2 = temp;

System.out.println("Pushed: " + x);

public int pop() {

if (q1.isEmpty()) {

System.out.println("Stack is empty!");

return -1;

return q1.remove();

public int top() {

if (q1.isEmpty()) {

System.out.println("Stack is empty!");
 return -1;

return q1.peek();

public boolean isEmpty() {

return q1.isEmpty();

public void display() {

if (q1.isEmpty()) {

System.out.println("Stack is empty!");

return;

System.out.println("Stack contents (top to bottom): " + q1);

public static void main(String[] args) {

Program2b stack = new Program2b();

Scanner sc = new Scanner(System.in);

int choice, value;

do {

System.out.println("\n1. Push\n2. Pop\n3. Top\n4. Display\n5. Exit");

System.out.print("Enter your choice: ");

choice = sc.nextInt();

switch (choice) {

case 1:

System.out.print("Enter value to push: ");

value = sc.nextInt();

stack.push(value);
 break;

case 2:

int popped = stack.pop();

if (popped != -1)

System.out.println("Popped: " + popped);

break;

case 3:

int top = stack.top();

if (top != -1)

System.out.println("Top element: " + top);

break;

case 4:

stack.display();

break;

case 5:

System.out.println("Exiting...");

break;

default:

System.out.println("Invalid choice.");

} while (choice != 5);

sc.close();

6a)

import java.util.HashMap;

import java.util.Scanner;
public class Program6a {

public static int[] twoSum(int[] nums, int target) {

HashMap<Integer, Integer> map = new HashMap<>();

for (int i = 0; i < nums.length; i++) {

int complement = target - nums[i];

if (map.containsKey(complement)) {

return new int[] { map.get(complement), i };

map.put(nums[i], i);

return new int[]{}; // This was misplaced before

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

System.out.print("Enter the number of elements in the array: ");

int n = sc.nextInt();

int[] nums = new int[n];

System.out.print("Enter the array elements: ");

for (int i = 0; i < n; i++) {

nums[i] = sc.nextInt();

System.out.print("Enter the target sum: ");

int target = sc.nextInt();

int[] result = twoSum(nums, target);

if (result.length == 0) {

System.out.println("No solution found.");

} else {
 System.out.println("Indices of the two numbers: [" + result[0] + ", " + result[1] + "]");

sc.close();

} }

Set -13a)

import java.util.*;

public class AssignCookies {

public static int findContentChildren(int[] greed, int[] cookies) {

Arrays.sort(greed);

Arrays.sort(cookies);

int i = 0, j = 0;

while (i < greed.length && j < cookies.length) {

if (cookies[j] >= greed[i]) {

i++;

j++;

return i;

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

System.out.println("Enter number of children:");

int n = sc.nextInt();
 int[] greed = new int[n];

System.out.println("Enter greed factors:");

for (int i = 0; i < n; i++) {

greed[i] = sc.nextInt();

System.out.println("Enter number of cookies:");

int m = sc.nextInt();

int[] cookies = new int[m];

System.out.println("Enter cookie sizes:");

for (int i = 0; i < m; i++) {

cookies[i] = sc.nextInt();

int result = findContentChildren(greed, cookies);

System.out.println("Maximum number of children that can be satisfied: " + result);

sc.close();

Set14

14a)

import java.util.*;

public class LemonadeStand {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

List<Integer> payments = new ArrayList<>();

System.out.println("Welcome to the Lemonade Stand!");

while (true) {

System.out.print("Enter payment amount of the customer (or type 'exit' to quit): ");

String input = sc.nextLine();

if (input.equalsIgnoreCase("exit")) break;

int payment = Integer.parseInt(input);

if (payment == 5) {

five++;

System.out.println("Customer served. Change given: 0");

} else if (payment == 10) {

if (five >= 1) {

five--;

ten++;

System.out.println("Customer served. Change given: 5");

} else {

System.out.println("Cannot give change. Transaction failed.");

break;

} else if (payment == 20) {

if (ten >= 1 && five >= 1) {

ten--;

five--;

System.out.println("Customer served. Change given: 15");

} else if (five >= 3) {

System.out.println("Customer served. Change given: 15");

} else {

System.out.println("Cannot give change. Transaction failed.");

break;

sc.close();

Set 17

17a)

import java.util.Scanner;

class Node {

int data;

Node left, right;

Node(int item) {

data = item;

left = right = null;

public class CountPathsBinaryTree {

public static int countPaths(Node root) {

return countPathsUtil(root, 0);

public static int countPathsUtil(Node root, int currentSum) {

if (root == null) {

return 0;

currentSum += root.data;

if (root.left == null && root.right == null) {

return 1;

return countPathsUtil(root.left, currentSum) + countPathsUtil(root.right, currentSum);

public static Node insert(Node root, int key) {

if (root == null) return new Node(key);

if (key < root.data)

root.left = insert(root.left, key);

else

root.right = insert(root.right, key);

return root;

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

Node root = null;

System.out.print("Enter number of nodes: ");

int n = sc.nextInt();
 System.out.println("Enter " + n + " node values:");

for (int i = 0; i < n; i++) {

int val = sc.nextInt();

root = insert(root, val);

int totalPaths = countPaths(root);

System.out.println("Total number of root-to-leaf paths: " + totalPaths);

For grid problem

import java.util.Scanner;

public class GridPaths {

static long factorial(int num) {

long result = 1;

for (int i = 2; i <= num; i++)

result *= i;

return result;

static long countPaths(int n, int m) {

return factorial(n + m) / (factorial(n) * factorial(m));

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

System.out.print("Enter n (rows): ");

System.out.print("Enter m (columns): ");

int m = sc.nextInt();

long totalPaths = countPaths(n, m);

System.out.println("Number of paths from (0,0) to (" + n + "," + m + "): " + totalPaths);

Enter n (rows): 2

Enter m (columns): 2

Number of paths from (0,0) to (2,2): 6

Set20

20a)

import java.util.Arrays;

import java.util.Scanner;

public class TripletCheckerDynamic {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

System.out.println("Enter the number of elements in the array:");

int n = scanner.nextInt();

int[] arr = new int[n];

System.out.println("Enter the elements of the array:");

for (int i = 0; i < n; i++) {

arr[i] = scanner.nextInt();

findTriplet(arr);
}

public static void findTriplet(int[] arr) {

Arrays.sort(arr); // Sort the array to use the two-pointer technique

int n = arr.length;

boolean found = false;

for (int i = 0; i < n - 1; i++) { // Loop through each element as the third element

int left = 0; // Left pointer starts from the beginning

int right = n - 1; // Right pointer starts from the last element

while (left < right) {

// Check if arr[i] is the sum of arr[left] and arr[right]

if (arr[i] == arr[left] + arr[right]) {

System.out.println("Triplet found: " + arr[left] + ", " + arr[right] + ", " + arr[i]);

found = true;

break; // Stop after finding the first triplet

} else if (arr[left] + arr[right] < arr[i]) {

left++; // Move left pointer to the right if sum is less than arr[i]

} else {

right--; // Move right pointer to the left if sum is greater than arr[i]

if (found) break; // Stop iterating if a triplet is found

if (!found) {
 System.out.println("No triplet found where the sum of two elements equals the third
element.");

Brute forcemethod

import java.util.Scanner;

public class TripletCheckerDynamic

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

System.out.println("Enter the number of elements in the array:");

int n = scanner.nextInt();

int[] arr = new int[n];

System.out.println("Enter the elements of the array:");

for (int i = 0; i < n; i++) {

arr[i] = scanner.nextInt();

checkTriplet(arr);

public static void checkTriplet(int[] arr) {

boolean found = false;

int length = arr.length;

for (int i = 0; i < length; i++) {

for (int j = i + 1; j < length; j++) {

for (int k = 0; k < length; k++) {

System.out.println(arr[i] + ", " + arr[j] + ", " + arr[k]);

found = true;

return; // Stop after finding the first triplet

if (!found) {

System.out.println("Triplet not exists");

Set 40 a

import java.util.Scanner;

public class StockTrading {

public static int maxProfit(int[] prices, int fee) {

// If there are no prices or only one price, no transaction can be made

if (prices == null || prices.length <= 1) {

return 0;

}
 int cash = 0; // Maximum profit when not holding a stock

int hold = -prices[0]; // Maximum profit when holding a stock

for (int i = 1; i < prices.length; i++) {

// Update cash: Either we don't sell or we sell after buying

cash = Math.max(cash, hold + prices[i] - fee);

// Update hold: Either we don't buy or we buy after selling previously held stock

hold = Math.max(hold, cash - prices[i]);

return cash; // The maximum profit is when we are not holding any stock

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

System.out.println("Enter the number of days:");

int n = scanner.nextInt();

int[] prices = new int[n];

System.out.println("Enter the stock prices for each day:");

for (int i = 0; i < n; i++) {

prices[i] = scanner.nextInt();

System.out.println("Enter the transaction fee:");

int fee = scanner.nextInt();

System.out.println("Maximum profit with transaction fee: " + profit);

Another method

import java.util.Scanner;

import java.util.Locale;

public class StockTrader {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in).useLocale(Locale.US); // Ensure decimal works with

String stockSymbol;

int quantity=0;

double purchasePrice = 0.0;

boolean hasStock = false;

System.out.println("Simple Stock Trading Simulation");

while (true) {

System.out.println("\nOptions:");

System.out.println("1. Buy Stock");

System.out.println("2. Sell Stock");

System.out.println("3. Exit");

System.out.print("Enter your choice: ");

int choice = scanner.nextInt();

scanner.nextLine(); // Consume newline

switch (choice) {
 case 1:

if (hasStock) {

System.out.println("You already own stock. Sell before buying more.");

break;

System.out.print("Enter the stock symbol: ");

stockSymbol = scanner.nextLine();

System.out.print("Enter the quantity to buy: ");

quantity = scanner.nextInt();

System.out.print("Enter the purchase price per share: ");

purchasePrice = scanner.nextDouble();

scanner.nextLine(); // Consume newline

System.out.println("Bought " + quantity + " shares of " + stockSymbol + " at $" +

hasStock = true;

break;

case 2:

if (!hasStock) {

System.out.println("You don't own any stock to sell.");

break;

System.out.print("Enter the selling price per share: ");

double sellingPrice = scanner.nextDouble();

scanner.nextLine(); // Consume newline

// Debugging - Print values before calculating profit

System.out.println("Debug - Purchase Price: " + purchasePrice);

System.out.println("Debug - Selling Price: " + sellingPrice);

// Ensure the variables are valid before calculating profit

if (purchasePrice < 0 || sellingPrice < 0 || quantity < 1) {

System.out.println("Invalid input. Prices and quantity should be positive numbers.");

break;

// Calculate profit/loss

double profit = (sellingPrice - purchasePrice) * quantity;

System.out.println("Sold " + quantity + " shares of the stock for $" + sellingPrice + " per
share.");

System.out.println("Profit/Loss: $" + String.format("%.2f", profit)); // Format to 2 decimal

hasStock = false;

purchasePrice = 0.0; // Reset purchase price

break;

case 3:

System.out.println("Exiting the simulation.");

scanner.close();

return;

default:

System.out.println("Invalid choice. Please try again.");