School Maths

 All formula

Useful questions for CSE Students

Leetcode:

• https://leetcode.com/problems/bulb-switcher-iii/
• https://leetcode.com/discuss/interview-question/406031/

Geeks:

• https://www.geeksforgeeks.org/max-count-of-unique-ratio-fraction-pairs-in-given-arrays/

Create custom Connection Pool class:

• https://www.baeldung.com/java-connection-pooling (point 4)

Graph DFS on real life scenario: 

Implement the class User, representing a person in a social network, with the following functionalities: 

Each user has a name. Provide a public constructor accepting that name.

 Users can befriend each other with the following method:

 public void befriend(User other)

Friendships are symmetric: a.befriend(b) is equivalent to b.befriend(a).

·       Clients can check whether two users are direct friends or indirect friends (friends of friends), using the following two methods,

public boolean isDirectFriendOf(User other)

public boolean isIndirectFriendOf(User other)

Solution:

Solution

import java.util.*;

public class User {

    private String name;

    private Set<User> friends = new HashSet<>();

    public User(String name) {

        this.name = name;

    }

    public void befriend(User other) {

        friends.add(other);

        other.friends.add(this);

    }

    public boolean isDirectFriendOf(User other) {

        return friends.contains(other);

    }

    //DFS

    public boolean isIndirectFriendOf(User other) {

        Set<User> visited = new HashSet<>();

        Stack<User> stack = new Stack<>();

        stack.push(this);

        while (!stack.isEmpty()) {

            User user = stack.pop();

            if (user.equals(other)) {

                return true;

            }

            if (visited.add(user)) {

                stack.addAll(user.friends);

            }

        }

        return false;

    }

    public static void main(String...args) {

        User a = new User("A"), 

             b = new User("B"),

             c = new User("C"),

             d = new User("D"),

             e = new User("E");

        a.befriend(b);

        a.befriend(c);

        d.befriend(c);

        e.befriend(a);

        System.out.println(b.isDirectFriendOf(c));

        System.out.println(b.isIndirectFriendOf(c));

        System.out.println(b.isIndirectFriendOf(d));

        System.out.println(b.isIndirectFriendOf(e));

    }

}

Useful Commands

 Very useful commands:

mvn dependency:tree -Dverbose > dependencyGraph.txt