Ruby Program to Count Words in String

You can count words in a string in Ruby using string.split.size, which splits the string by spaces and counts the resulting words.

Examples

InputHello world

Output2

InputRuby is fun to learn

Output5

Input

Output0

How to Think About It

To count words in a string, first split the string into parts where spaces separate words. Then count how many parts you have. This works because each word is separated by spaces, so splitting by space gives all words as separate pieces.

Algorithm

1

Get the input string

2

Split the string into words using spaces as separators

3

Count the number of words obtained

4

Return or print the count

Code

ruby

puts "Enter a string:"
input = gets.chomp
word_count = input.split.size
puts "Number of words: #{word_count}"

Output

Enter a string:
Hello Ruby world
Number of words: 3

Dry Run

Let's trace the input 'Hello Ruby world' through the code

1

Input string

input = 'Hello Ruby world'

2

Split string

input.split => ['Hello', 'Ruby', 'world']

3

Count words

word_count = 3

4

Print result

Output: 'Number of words: 3'

Step	Value
Input string	Hello Ruby world
Split result	['Hello', 'Ruby', 'world']
Word count	3

Why This Works

Step 1: Splitting the string

The split method breaks the string into an array of words using spaces as separators.

Step 2: Counting words

The size method counts how many elements (words) are in the array.

Step 3: Outputting the count

The program prints the number of words found in the string.

Alternative Approaches

Using scan with regex

ruby

puts "Enter a string:"
input = gets.chomp
word_count = input.scan(/\w+/).size
puts "Number of words: #{word_count}"

This counts words by matching word characters, which can handle punctuation better but is slightly more complex.

Using count with split and reject

ruby

puts "Enter a string:"
input = gets.chomp
words = input.split.reject(&:empty?)
word_count = words.size
puts "Number of words: #{word_count}"

This method removes empty strings after splitting, useful if the string has multiple spaces.

Complexity: O(n) time, O(n) space

Time Complexity

Splitting the string scans each character once, so it takes linear time relative to the string length.

Space Complexity

The split method creates an array of words, which requires space proportional to the number of words.

Which Approach is Fastest?

Using split.size is fastest and simplest for most cases; regex scanning is more flexible but slightly slower.

Approach	Time	Space	Best For
split.size	O(n)	O(n)	Simple word counts with spaces
scan with regex	O(n)	O(n)	Counting words with punctuation
split + reject	O(n)	O(n)	Handling extra spaces cleanly