Zip for combining arrays in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code using zip?

Consider the following Ruby code that uses zip to combine arrays. What will it print?

Ruby

a = [1, 2, 3]
b = ['a', 'b', 'c']
result = a.zip(b)
puts result.inspect

A [[1, "a"], [2, "b"]]

B [[1, "a"], [2, "b"], [3, "c"]]

C [[1, "a"], [2, "b"], [3, nil]]

D [[1, 2, 3], ["a", "b", "c"]]

💡 Hint

Remember that zip pairs elements by their index from each array.

The zip method pairs elements from each array by their index. Since both arrays have 3 elements, the result is an array of 3 pairs.

❓ Predict Output

intermediate

What happens when arrays of different lengths are zipped?

Look at this Ruby code where arrays of different lengths are zipped. What is the output?

Ruby

x = [10, 20]
y = ['x', 'y', 'z']
result = x.zip(y)
puts result.inspect

A [[10, "x"], [20, "y"]]

B [[10, "x"], [20, "y"], [nil, "z"]]

C [[10, "x"], [20, "y"], [20, "z"]]

D [[10, "x"], [20, "y"], [nil, nil]]

💡 Hint

The length of the resulting array matches the receiver array's length.

The zip method returns an array with the same length as the first array. Extra elements in the second array are ignored.

🔧 Debug

advanced

Why does this zip code raise an error?

Examine this Ruby code snippet. It raises an error. What is the cause?

Ruby

a = [1, 2, 3]
b = nil
result = a.zip(b)
puts result.inspect

A ArgumentError because <code>zip</code> expects arrays only

B TypeError because <code>nil</code> cannot be converted to array

C NoMethodError because <code>nil</code> does not respond to <code>to_ary</code>

D SyntaxError due to wrong method call

💡 Hint

Think about what zip does internally with its arguments.

The zip method tries to convert arguments to arrays using to_ary. Since nil does not have this method, it raises NoMethodError.

🧠 Conceptual

advanced

How does zip behave with a block?

What is the output of this Ruby code that uses zip with a block?

Ruby

a = [1, 2, 3]
b = ['x', 'y', 'z']
a.zip(b) { |num, char| puts "#{num}-#{char}" }

A

Prints:
1-x
2-y
3-z
and returns nil

B

Prints:
[1, "x"]
[2, "y"]
[3, "z"]
and returns the zipped array

C Prints nothing and returns the zipped array

D

Prints:
1-x
2-y
3-z
and returns the zipped array

💡 Hint

Remember what zip returns when given a block.

When zip is called with a block, it yields each combined array to the block and returns nil.

🚀 Application

expert

How many pairs are in the zipped array?

Given these arrays, how many pairs will the zipped array contain?

Ruby

arr1 = [5, 10, 15, 20]
arr2 = ['a', 'b']
arr3 = [:x, :y, :z]
result = arr1.zip(arr2, arr3)

A 1 pair

B 3 pairs

C 2 pairs

D 4 pairs

💡 Hint

The number of pairs equals the length of the first array.

The zip method returns an array with the same length as the first array, pairing elements from all given arrays by index.