Split and join methods in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of splitting a string with multiple spaces

What is the output of this Ruby code?

Ruby

text = "apple  banana   cherry"
result = text.split(" ")
puts result.inspect

A ["apple", " banana", " cherry"]

B ["apple", "banana", "cherry"]

C ["apple banana cherry"]

D ["apple", "", "banana", "", "", "cherry"]

💡 Hint

The split method with a space splits exactly on each space character.

Using split(" ") splits the string at every single space, so multiple spaces create empty strings in the array.

❓ Predict Output

intermediate

Joining array elements with a custom separator

What is the output of this Ruby code?

Ruby

arr = ["red", "green", "blue"]
result = arr.join("-")
puts result

A red green blue

B red,green,blue

C red-green-blue

D redgreenblue

💡 Hint

The join method uses the string you give as a separator between elements.

The join method combines array elements into one string, placing the given separator between them.

🔧 Debug

advanced

Why does this split produce an empty first element?

Consider this Ruby code. Why does the first element of the result array become an empty string?

Ruby

text = ",one,two,three"
result = text.split(",")
puts result.inspect

A Because the string starts with the separator, split creates an empty string before the first comma.

B Because split removes the first element if it is empty.

C Because split ignores separators at the start of the string.

D Because split treats commas as part of the first element.

💡 Hint

Think about what happens before the first comma.

When the string starts with the separator, split returns an empty string for the part before the first separator.

❓ Predict Output

advanced

Splitting with limit parameter

What is the output of this Ruby code?

Ruby

text = "a,b,c,d"
result = text.split(",", 3)
puts result.inspect

A ["a", "b", "c", "d"]

B ["a", "b", "c,d"]

C ["a,b", "c", "d"]

D ["a", "b,c", "d"]

💡 Hint

The limit parameter controls how many parts the string is split into.

With limit 3, split divides the string into at most 3 parts, so the last part contains the rest of the string.

🧠 Conceptual

expert

Effect of split and join on string with multiple separators

Given the Ruby code below, what is the final output?

Ruby

text = "one,,two,,,three"
parts = text.split(",")
joined = parts.join(",")
puts joined

A one,,two,,,three

B one,two,three

C one,,two,,three

D one,two,,three

💡 Hint

Think about how split handles consecutive separators and what join does with empty strings.

Split creates empty strings for consecutive commas, and join puts commas back between all elements, preserving the original pattern.

Practice

1. What does the Ruby method split do when called on a string?

easy

A. It divides the string into an array based on a separator.

B. It combines array elements into a single string.

C. It changes all characters to uppercase.

D. It removes spaces from the string.

Solution

1. Step 1: Understand the purpose of split

   The split method breaks a string into parts wherever a separator is found.

2. Step 2: Identify the output type

   After splitting, the output is an array containing the separated parts of the string.

3. Final Answer:

   It divides the string into an array based on a separator. -> Option A

4. Quick Check:

   split = divide string into array [OK]

Hint: Split cuts strings into arrays at separators [OK]

Common Mistakes:

• Thinking split joins array elements
• Confusing split with uppercase conversion
• Assuming split removes spaces without separator

2. Which of the following is the correct syntax to join an array ["a", "b", "c"] into a string separated by dashes in Ruby?

easy

A. ["a", "b", "c"].split("-")

B. ["a", "b", "c"].join("-")

C. "a-b-c".join(["a", "b", "c"])

D. "a-b-c".split(["a", "b", "c"])

Solution

1. Step 1: Identify the method to combine array elements

   The join method is used on arrays to create a string with a separator.

2. Step 2: Check the syntax for join with a separator

   The syntax is array.join(separator), so ["a", "b", "c"].join("-") is correct.

3. Final Answer:

   ["a", "b", "c"].join("-") -> Option B

4. Quick Check:

   join(array) with separator = correct syntax [OK]

Hint: Use array.join(separator) to combine elements [OK]

Common Mistakes:

• Using split instead of join to combine
• Calling join on a string instead of array
• Passing array as argument to split or join incorrectly

3. What is the output of this Ruby code?

sentence = "apple,banana,cherry"
fruits = sentence.split(",")
result = fruits.join(" & ")
puts result

medium

A. apple & banana & cherry

B. apple,banana,cherry

C. apple banana cherry

D. ["apple", "banana", "cherry"]

Solution

1. Step 1: Split the string by commas

   The split(",") breaks the string into ["apple", "banana", "cherry"].

2. Step 2: Join the array with " & " separator

   The join(" & ") combines the array elements into the string "apple & banana & cherry".

3. Final Answer:

   apple & banana & cherry -> Option A

4. Quick Check:

   split then join with & = apple & banana & cherry [OK]

Hint: Split by comma, join with & gives 'apple & banana & cherry' [OK]

Common Mistakes:

• Expecting original string without changes
• Confusing split and join order
• Thinking join adds commas automatically

4. The following Ruby code is intended to split a string into words and then join them with a space, but it raises an error. What is the problem?

text = "hello world"
words = text.split
joined = words.join
puts joined()

medium

A. The variable words is not an array.

B. The method split requires an argument.

C. The call joined() is incorrect syntax.

D. The join method cannot be called without a separator.

Solution

1. Step 1: Check the method calls

   split without arguments splits on whitespace correctly. join can be called without arguments to join with empty string.

2. Step 2: Identify the error in puts joined()

   In Ruby, calling a variable like a method with parentheses joined() causes an error because joined is a string, not a method.

3. Final Answer:

   The call joined() is incorrect syntax. -> Option C

4. Quick Check:

   Calling string like method with () = error [OK]

Hint: Don't add () when printing variables in Ruby [OK]

Common Mistakes:

• Thinking split needs an argument always
• Assuming join requires a separator
• Calling variables as methods with parentheses

5. Given a string data = "red;green;blue;yellow", write Ruby code to split it into an array, remove the color "blue", and then join the remaining colors with commas. What is the correct output?

hard

A. "red;green;yellow"

B. "red,green,blue,yellow"

C. "red green yellow"

D. "red,green,yellow"

Solution

1. Step 1: Split the string by semicolons

   Using split(";") on data gives ["red", "green", "blue", "yellow"].

2. Step 2: Remove "blue" from the array

   Remove "blue" by using array.delete("blue") or array.reject!.

3. Step 3: Join the remaining elements with commas

   Joining with join(",") results in "red,green,yellow".

4. Final Answer:

   "red,green,yellow" -> Option D

5. Quick Check:

   Split by ;, remove blue, join by , = red,green,yellow [OK]

Hint: Split by ; remove item, join by , for final string [OK]

Common Mistakes:

• Forgetting to remove "blue" before joining
• Joining with wrong separator
• Using split without argument or wrong separator