TwitSplit

Zalora pre-interview assignment

Requirement

If you're curious enough please contact Zalora to know exactly the problem.

System

• iOS >= 10.3
• Swift 3.0

What I've done

• TwitSplit algorithm.
• Unit test.
• Documentation.

How TwitSplit works?

1st approach: Using regexes

Let take a look on failure cases to know why regexes is wrong approach. Checkout here

• Be not able to split a message what is longer than 10 parts (50 characters per part)
• Be not able to re-calculate total parts after indicator increases. For example, 1/10 (4 characters) vs 10/10 (5 characters)
• Be not able to append last word into new partial.
• Many anothers test cases

2nd approach: Using recursive, re-calculate total part, re-render prefix indicator

• Step 1: Condensed whitespaces and newlines characters from input message.
• Step 2: Return original input message if it's less than limit characters.
• Step 3: Estimate total partial before separate.
• Step 4: Seperate input message into individual words by checking each word's length should greater than limit.
• Step 5: Render all partials.

Checkout split function

Render all partials

• Step 5.1: Append indicator as prefix of partials.
• Step 5.2: Go through individual word.
• Step 5.3: Return empty array if the length of individual word include indicator greater than limit.
• Step 5.4: Skip words that already joined into partial. Then, pre-calculate how much partial's length before join.
• Step 5.5: Break loop if partial's length is over than limit.
• Step 5.6: Append individual word.
• Step 5.7: Store current index where the last word is appended.

=> Applied recursive to re-calculate total partials, if it still remains words, else return.

Checkout joinedPartial function

Time complexity

In general, the time complexity is O(n2). Follow this formula to calculate estTotal

estTotal = inputMessage’s length / limit + 1

So, the estTotal changes while input message's length is changed, and the worst case scenario happens if limit equal to 1. Then we need to loop through estTotal * inputMessage's length times.

// Go through 0 to total partial
for i in 0..<estTotal {
    //...
    //...
            
    // Go through individual word
    for (index, item) in words.enumerated() {
        //...
        //...
    }
}

What I haven't finished yet

• TwitSplit application.