Swift Coding Test Course, Card Sorting

Problem

You need to sort specific cards. Each card may contain numbers and letters. Sort the given cards according to the following rules:

Letter cards must come before number cards.
For letter cards, sort them in alphabetical order.
For number cards, sort them in ascending order.

For example, if the given cards are ["A", "3", "B", "1", "2"], the result will be ["A", "B", "1", "2", "3"].

Solution Process

Step 1: Understanding the Problem

This problem involves separating the cards into letter cards and number cards and sorting them. You need to apply specific rules according to the requirements of the problem.

Step 2: Choosing a Data Structure

In Swift, you can use an array to store and manipulate the cards. Work based on the array provided as input.

Step 3: Setting Sorting Criteria

After separating letter cards and number cards, you need to define how to sort each of them. This will allow you to achieve the final result.

Step 4: Writing Swift Code

            
            import Foundation

            func sortCards(cards: [String]) -> [String] {
                var letters: [String] = []
                var numbers: [Int] = []

                // Separate cards
                for card in cards {
                    if let number = Int(card) {
                        numbers.append(number)
                    } else {
                        letters.append(card)
                    }
                }

                // Sort
                letters.sort()
                numbers.sort()

                // Combine results
                let sortedNumbers = numbers.map { String($0) }
                return letters + sortedNumbers
            }

            // Example
            let cards = ["A", "3", "B", "1", "2"]
            let sortedCards = sortCards(cards: cards)
            print(sortedCards) // ["A", "B", "1", "2", "3"]

Step 5: Analyzing Time Complexity

The time complexity of this algorithm is O(n log n). This is because both string sorting and number sorting have a time complexity of O(n log n). If we let n be the number of cards, in the worst case, up to n cards may be given, ensuring sufficient performance.

Step 6: Conclusion

This problem allows you to learn about basic array handling and sorting techniques in Swift. Additionally, understanding how to handle strings and numbers is important. Practicing problems like this can help you in coding interviews.