In this post, we will learn about arrays and the operations we can perform on them.
Array is the most common data structures we use in our programs. They are used to store data that can be accessed using index. In Ruby, an array may contain different type of data unlike in Java and C# where array stores similar type of data.
The starting value of array index in Ruby is 0 whereas the ending value is size of array – 1.
To declare an array, we use:
Syntax
array_name = Array.new([ .. ])
or
array_name = []
A blank array with 5 elements can be declared as:
array_name = Array.new(5)
All of the 5 values would be null in this case. If you want to initialize all values with some default value, use:
array_name = Array.new( 5, 0 )
All the array values will be 0 now.
Let us see some examples:
Calculating sum of even numbers
numbers = [1,2,3,4,5,6]
sum = 0
numbers.each do |x|
if x%2 ==0 then
sum += x
end
end
puts sum
Same program using for loop
numbers = [1,2,3,4,5,6]
sum = 0
for i in 0..numbers.size-1
if numbers[i]%2 == 0 then
sum += numbers[i]
end
end
puts sum
Adding items to array
We can add items to an existing array using any of the following methods:
numbers = [1,2,3,4] numbers << 5 # adds item to the end of array numbers.push(5) # adds item to the end of array numbers.unshift(5) # adds item to the start of array
Removing elements from array
To remove an item from array, we can use:
numbers = [10,20,30,40] numbers.pop # removes 40 numbers.shift # removes 10 numbers.delete_at(2) # removes the value 30
Combining array
We can easily combine two arrays by using the + operator. Here is an example:
numbers1 = [1,2,3] numbers2 = [4,5,6] numbers = numbers1 + numbers2 puts numbers
We can also write:
numbers = numbers1 + numbers2
as
numbers = numbers1.concat(numbers2)
We can also subtract one array from another.
numbers1 = [1,2,3,4] numbers2 = [2,3,8] numbers = numbers1 - numbers2
Output:
[1,4]
Reversing and rotating array
We can easily rotate or reverse an array. Here are some examples:
numbers = [1,2,3,4,5] numbers.reverse! # [5,4,3,2,1] ! means modify original array instead of returning number.rotate! # [2,3,4,5,1] number.rotate!(-1) # [5,1,2,3,4]
Removing duplicate values
We can remove duplicate values from array by calling the method uniq. Here is an example:
numbers = [1,2,3,1,5,2] numbers.uniq!