HashRevision.rb

# In this challenge, we will show you ways in which we can add key-value pairs to Hash objects, delete keys from them, and retain them based on a logic.

# Consider the following Hash object:

h = Hash.new
h.default = 0

# A new key-value pair can be added using or the store method

h[key] = value

# or

h.store(key, value) # .store is a method of Hash class

# An existing key can be deleted using the delete method

h.delete(key) # .delete is a method of Hash class


# For destructive selection and deletion, we can use keep_if and delete_if as seen in Array-Selection

h = {1 => 1, 2 => 4, 3 => 9, 4 => 16, 5 => 25}
#  => {1 => 1, 2 => 4, 3 => 9, 4 => 16, 5 => 25}
h.keep_if {|key, value| key % 2 == 0} 
# or
 h.delete_if {|key, value| key % 2 != 0}
#  => {2 => 4, 4 => 16}
# Note

# For non-destructive selection or rejection, we can use select, reject, and drop_while similar to Array-Selection

# In this challenge, a hash object called hackerrank is already created. You have to add

# A key-value pair [543121, 100] to the hackerrank object using store
# Retain all key-value pairs where keys are Integers ( clue : is_a? Integer )
# Delete all key-value pairs where keys are even-valued.

hackerrank.store(543121, 100)

hackerrank.keep_if {|key, value| key % 1 == 0}
# or
hackerrank.keep_if{|key,value| key.is_a?Integer}

hackerrank.delete_if {|key, value| key % 2 == 0}