Sorted and custom comparators in Swift - Step-by-Step Execution

Concept Flow - Sorted and custom comparators

Start with array

↓

Call sorted()

↓

Check if custom comparator provided?

No→Use default ascending order

Yes↓

Use custom comparator to compare elements

↓

Sort elements accordingly

↓

Return sorted array

↓

End

The array is sorted by calling sorted(). If a custom comparator is given, it compares elements using that; otherwise, it sorts in ascending order.

Execution Sample

Swift

let numbers = [3, 1, 4, 2]
let sortedAsc = numbers.sorted()
let sortedDesc = numbers.sorted { $0 > $1 }

Sorts an array ascending by default, then descending using a custom comparator.

Execution Table

Step	Action	Comparator Used	Comparison Example	Resulting Array
1	Start with array	N/A	N/A	[3, 1, 4, 2]
2	Call sorted() without comparator	Default ascending	Compare 3 and 1: 3 > 1	[1, 2, 3, 4]
3	Call sorted() with custom comparator	Custom: $0 > $1 (descending)	Compare 3 and 1: 3 > 1 is true	[4, 3, 2, 1]
4	End	N/A	N/A	Sorted arrays ready

💡 Sorting completes after comparing all elements using the chosen comparator.

Variable Tracker

Variable	Start	After sorted()	After sorted { $0 > $1 }
numbers	[3, 1, 4, 2]	[3, 1, 4, 2]	[3, 1, 4, 2]
sortedAsc	N/A	[1, 2, 3, 4]	[1, 2, 3, 4]
sortedDesc	N/A	N/A	[4, 3, 2, 1]

Key Moments - 3 Insights

Why does sorted() without a comparator sort in ascending order?

By default, sorted() uses the natural order of elements (like numbers from smallest to largest), as shown in step 2 of the execution_table.

How does the custom comparator { $0 > $1 } change sorting?

It tells sorted() to put bigger numbers first by comparing if the first element is greater than the second, reversing the order (step 3).

Does the original array change after sorting?

No, sorted() returns a new sorted array and leaves the original array unchanged, as seen in variable_tracker where 'numbers' stays the same.

Visual Quiz - 3 Questions

Look at the execution_table, what is the array after calling sorted() without a comparator?

A [4, 3, 2, 1]

B [1, 2, 3, 4]

C [3, 1, 4, 2]

D [2, 3, 1, 4]

💡 Hint

Check step 2 in the execution_table under 'Resulting Array'.

At which step does the sorting use the custom comparator?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look for the step mentioning 'custom comparator' in the execution_table.

If the comparator was changed to { $0 < $1 }, how would the sorted array change?

A It would sort descending

B It would not sort

C It would sort ascending

D It would reverse the array

💡 Hint

The comparator { $0 < $1 } means smaller elements come first, like the default ascending order.

Concept Snapshot

sorted() returns a new sorted array.
By default, it sorts ascending.
Custom comparator closure defines order.
Comparator returns true if first element should come before second.
Original array stays unchanged.
Use sorted(by:) for custom sorting.

Full Transcript

This example shows how to sort arrays in Swift using sorted(). First, the array [3, 1, 4, 2] is sorted ascending by default, producing [1, 2, 3, 4]. Then, a custom comparator { $0 > $1 } is used to sort descending, producing [4, 3, 2, 1]. The original array remains unchanged. The flow starts with the array, calls sorted(), checks if a custom comparator is provided, uses it if yes, sorts accordingly, and returns the sorted array. Variables track the original and sorted arrays. Key points include default ascending order, how the comparator changes sorting, and that sorted() returns a new array without modifying the original.