Day 28: RegEx, Patterns, and Intro to Databases - HackerRank 30 days of code solution

Objective
Today, we're working with regular expressions.

Task
Consider a database table, Emails, which has the attributes First Name and Email ID. Given  rows of data simulating the Emails table, print an alphabetically-ordered list of people whose email address ends in .

Input Format

The first line contains an integer, , total number of rows in the table.
Each of the  subsequent lines contains  space-separated strings denoting a person's first name and email ID, respectively.

Constraints

• Each of the first names consists of lower case letters  only.
• Each of the email IDs consists of lower case letters ,  and  only.
• The length of the first name is no longer than 20.
• The length of the email ID is no longer than 50.

Output Format

Print an alphabetically-ordered list of first names for every user with a gmail account. Each name must be printed on a new line.

Sample Input

6
riya riya@gmail.com
julia julia@julia.me
julia sjulia@gmail.com
julia julia@gmail.com
samantha samantha@gmail.com
tanya tanya@gmail.com

Sample Output

julia
julia
riya
samantha
tanya

Solution :

import java.io.*;

import java.util.*;

import java.text.*;

import java.math.*;

import java.util.regex.*;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Scanner;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class Solution {

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);

        int N = in.nextInt();

        String emailRegEx = ".+@gmail\\.com$";

        Pattern pattern = Pattern.compile(emailRegEx);

        ArrayList<String> list = new ArrayList<>();

        for (int i = 0; i < N; i++) {

            String name = in.next();

            String email = in.next();

            Matcher matcher = pattern.matcher(email);

            if (matcher.find()) list.add(name);

        }

        Collections.sort(list);

        list.forEach(System.out::println);

    }

}