1-Warmup-Problems

Warmup Ruby Problems

You can find solutions here:

• In procedural_solutions.rb are our first attempts at writing Ruby. Almost everything is written with while and if
• In good_solutions.rb we do a rekate on everything with our knowledge of Enumerable

In a file called warmup.rb, solve the following problems:

Factorial

Implement the factorial function fact(n).

• Implement it using a simple loop
• Implement it using recursion

Lucas series

Because Fibonacci is way too trivial, implement the following functions that work with Lucas series:

• nth_lucas(n) -> returns the nth Lucas number
• first_lucas(n) -> returns a list of the first n Lucas numbers

Quick hint:

L(0) = 2
L(1) = 1
L(n) = L(n-1) + L(n-2)

Working with digits

Those are classic problems for using module division:

• Given an integer n, return the number of digits in n -> count_digits(n)
• Given an integer n, return the sum of all digits in n -> sum_digits(n)
• factorial_digits(n) -> for example, if we have 145, we need to calculate 1! + 4! + 5!

Fibonacci number

Implement a function, called fib_number(n), which takes an integer n and returns a number, which is formed by concatenating the first n Fibonacci numbers.

Examples:

fib_number 3 == 112
fib_number 10 == 11235813213455

Hack Numbers

A hack number is an integer, that matches the following criteria:

• The number, represented in binary, is a palindrome
• The number, represented in binary, has an odd number of 1's in it

Example of hack numbers:

• 1 is 1 in binary
• 7 is 111 in binary
• 7919 is 1111011101111 in binary

Implement the following functions:

• hack?(n) -> checks if n is a hack number
• next_hack(n) -> returns the next hack number, that is bigger than n

Few examples:

hack? 1 == true
next_hack 0 == 1

hack? 21 == true
next_hack 10 == 21

hack? 8191 == true
next_hack 8031 == 8191

Vowels in a string

Implement a function, called count_vowels(str), which returns the count of all vowels in the string str.

Count uppercase vowels aswell!

The English vowels are aeiouy.

Examples:

count_vowels "Python" == 2
count_vowels "Theistareykjarbunga" ==  8
count_vowels "grrrrgh!" == 0
count_vowels "Github is the second best thing that happend to programmers, after the keyboard!" == 22
count_vowels "A nice day to code!" == 8

Consonants in a string

Implement a function, called count_consonants str), which returns the count of all consonants in the string str.

Count uppercase consonants as well!

The English consonants are bcdfghjklmnpqrstvwxz.

Examples:

count_consonants "Python" == 4
count_consonants "Theistareykjarbunga" == 11
count_consonants "grrrrgh!" == 7
count_consonants "Github is the second best thing that happend to programmers, after the keyboard!" == 44
count_consonants "A nice day to code!" == 6

Palindrome Score

We denote the "Palindrome score" of an integer by the following function:

• P(n) = 1, if n is palindrome
• P(n) = 1 + P(s) where s is the sum of n and the reverse of n

Implement a function, called p_score(n), which finds the palindrome score for n.

Lets see two examples:

• p_score(121) = 1, because 121 is a palindrome.
• p_score(48) = 3, because:

1. P(48) = 1 + P(48 + 84) = 132
2. P(132) = 1 + 1 + P(132 + 321 = 363)
3. P(363) = 1.
4. When we return from the recursion, we get 3.

Examples:

p_score 121 == 1
p_score 48 == 3
p_score 198 == 6

Object palindomes

A palindrome is a word, phrase, number, or other sequence of characters which reads the same backward or forward.

Implement the following function: palindrome?(obj) that checks if the given obj is palindrome.

Examples:

palindrome? 121 == true
palindrome? 123 == false
palindrome? 'kapak' == true
palindrome? 'baba' == false
palindrome? 'azobi4amma4iboza' == true

Prime numbers

The usual deal. Implement the following functions:

• Check if number is prime -> prime?(n)
• List the first n prime numbers -> first_primes(n)
• OPTIONAL: List the first n prime numbers, using the Sieve of Eratosthenes

Sum all numbers in a given string

You are given a string, where there can be numbers. Return the sum of all numbers in that string (not digits, numbers)

Examples:

sum_of_numbers_in_string "1111" == 1111
sum_of_numbers_in_string "1abc33xyz22" == 1 + 33 + 22 = 56
sum_of_numbers_in_string "abcd" == 0

Anagrams

Here is the explanation of what an Anagram is - http://en.wikipedia.org/wiki/Anagram

Implemenent the following functions:

• anagrams?(a, b) - returns true, if the string a is an anagram of b

Is number balanced?

A number is called balanced, if we take the middle of it and the sums of the left and right parts are equal.

For example, the number 1238033 is balanced, because it's left part is 123 and right part is 033.

We have : 1 + 2 + 3 = 0 + 3 + 3 = 6.

A number with only one digit is always balanced!

Implement the function balanced?(n) that checks if n is balanced.

Few examples:

balanced?(9) == True
balanced?(11) == True
balanced?(13) == False
balanced?(121) == True
balanced?(4518) == True
balanced?(28471) == False
balanced?(1238033) == True

Zero Insertion

Given an integer, implement the function zero_insert(n), which returns a new integer, constructed by the following algorithm:

• If two neighboring digits are the same (like 55), insert a 0 between them (505)
• Also, if we add two neighboring digits and take their module by 10 (% 10) and the result is 0 - add 0 between them.

For example, if we have the number 116457, result will be: 10160457:

• 1 and 1 are the same, so we insert 0 between them
• 6 + 4 % 10 = 0, so we insert 0 between them.

Few examples:

zero_insert(116457) == 10160457
zero_insert(55555555) == 505050505050505
zero_insert(1) == 1
zero_insert(6446) == 6040406