# Word Frequency

Write a bash script to calculate the frequency of each word in a text file words.txt.
For simplicity sake, you may assume:
words.txt contains only lowercase characters and space ' ' characters. Each word must consist of lowercase characters only. Words are separated by one or more whitespace characters. Example:
Assume that words.txt has the following content:
the day is sunny the the the sunny is is Your script should output the following, sorted by descending frequency:

# Valid Phone Numbers

Given a text file file.txt that contains a list of phone numbers (one per line), write a one-liner bash script to print all valid phone numbers.
You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)
You may also assume each line in the text file must not contain leading or trailing white spaces.
Example:

# 10001st prime

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.
What is the 10 001st prime number?
At first glance, a simple iteration whilst checking if index position is prime, would suffice.
A pseudocode attempt:
sum = 0 for i = 2; i <= ?; i++ { if(isPrime(i)){ sum++ if ( sum >= 10001) { return i } } } Using the solution in go to check if is prime from former examples:

# Sum square difference

The sum of the squares of the first ten natural numbers is,
$$ 1^x1D2 + 2^2 + … + 10^2 = 385 $$
The square of the sum of the first ten natural numbers is,
$$ (1 + 2 + … + 10)^2 = 552 = 3025 $$
Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 − 385 = 2640.

# Smallest multiple

2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.
What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?
At first glance, and as a concept refresher, we’ll have to use *

*GCD*and**LCM**. GCD stands for Greatest Common Divisor. GCD is the largest number that divides the given numbers.# Largest palindrome product

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
Find the largest palindrome made from the product of two 3-digit numbers
The first observation is that the number should be in the range of 10000 and 998001. There’s a couple aproaches to the problem, such as:
Multiplicating two 3-digit numbers and checking the result if its a palindrome Creating palindromes and getting the factors to see if that pair is what we’re looking for.

# Largest prime factor

The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
We neeed to find the largest prime factor of 600851475143.
We know that the largest prime factor of a number, its the number itself.
As a concept refresher, any prime number is only divisible by 1 ant itself, thus, when dividing by a certain number, there should not be a reminder.

# Even Fibonacci numbers

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, …
By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
package main import ( "fmt" "time" ) func main() { start := time.

# Multiples of 3 and 5

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000.
package main import "fmt" func main() { sum := 0 for i := 0; i < 1000; i++ { if i % 3 == 0 || i % 5 == 0 { sum += i } } fmt.