• Break a large problem down into smaller steps using pseudocode
• Iterate through data structures and manipulate the content
• Determine which data structure (arrays or hashes) to use based on challenge requirements

The method calculate_mode will take an List of numbers or strings as its input and return an List of the most frequent values.

If there's only one most-frequent value, it returns a single-element List.

For example:

calculate_mode([1,2,3,3])         # => [3]
calculate_mode([4.5, 0, 0])       # => [0]
calculate_mode([1.5, -1, 1, 1.5]) # => [1.5]
calculate_mode([1,1,2,2])         # => [1,2]
calculate_mode([1,2,3])           # => [1,2,3], because all occur with equal frequency
calculate_mode(["who", "what", "where", "who"]) # => ["who"]

Remember to always write tests!