# Aayush Lal Roy | 2+ yrs exp
- Good with coding question. DS/algo.
- DB design is aldo good.
- Can proceed with next round
- Php, java, Ruby on rails, nodejs
- MySQL
- Messaging Queue - SQS
- AWS - SNS, EC2, S3

# Question 1:

array - ['a', 'b', 'c']

abc
acb
bac
bca
cab
cba

// logic

public class Scramble {
    public static void main(String args[]) {
        String arr[] = new String[]; //original array
        String arr1[] = new String[fact(arr.length)];
        scramble(arr, arr1, 0);
        for (String s : arr1) {
            System.out.println(s);
        }
    }

    public static void scramble(String arr[], String arr1[], int element) {
        if (arr.length() == 1) {
            return arr[0];
        }

        for (int i = 0; i < arr.length; i++) {
            int newArr[] = new int[arr.length - 1];
            count = 0;
            for (int j = 0; j <= arr.length; j++) {
                if (j == i) {
                    continue;
                } else {
                    newArr[count++] = arr[j];
                }
            }

            String s1 = scramble(newArr, arr1, i);
            arr1[i] = s1 + arr[i];
        }
    }
    
    public static int fact(int len) {
        int factorial = 1;
        for (int i = 1; i <= len; i++) {
            factorial *= i;
        }
        
        return factorial;
    }
}

# Question 2: DB

User service
Chat service
- 1<>1 chat
- text chat

- list of conversations, sorted
- list of messages. sorted,

- id
- created_at
- modified_at
- created_by_user_id
- modified_by_user_id
- soft_deleted

#Tables:

- coversations
- name
- profile_photo_link
- metadata
- is_group

- user_conversation_mapping:
- group_id
- user_id

- messages:
- text
- conversation_id:

Select * from conversations where user_id_1 = 123 OR user_id_2 = 123 order by modified_at desc limit 50 offset 0;