How do I retrieve a value of an array and compute it to a constant

Question

this problem appeared in one of my code challenge
```while.swift
let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0
// Enter your code below
while counter < numbers.count {
    print(numbers.count)
    counter++
}
```

Martin Wildfeuer · Accepted Answer

Hey there!
Values of an array at a certain index can be retrieved via subscripting. See Apple Swift docs: Accessing and Modifying an Array (https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/CollectionTypes.html#//apple_ref/doc/uid/TP40014097-CH8-ID105). I have added the approach with comments below.
```swift2.swift
let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0
// Loop as long as counter is less than the number of Ints in the array.
// Why less than? Arrays are zero based, in our case valid indices are
// 0, 1, 2, 3, 4, 5, 6. Count will give you seven, as there are seven Ints in our array
while counter < numbers.count {
// Add the value of the Int at the index `counter` to `sum`
// You can access values of an array at a specific index via subscripting,
// array[index]. You should always make sure that the index exists. If your
// index is out of range, this will result in a crash
sum += numbers[counter]

// Increment counter by one, otherwise we will end up
// with an infinite loop. Please note that `++` and `--`
// are deprecated in Swift 3. See the example below for the
// Swift3 version.
counter++
}
```
swift3.swift
// ...
while counter < numbers.count {
    sum += numbers[counter]
    counter += 1
}

Hope that helps :)

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Neerav Aiyappa

Neerav Aiyappa

How do I retrieve a value of an array and compute it to a constant

1 Answer

Martin Wildfeuer

Martin Wildfeuer