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arraysswift
Adrian
Adrian

Reputation: 16715

Swift: Excluding a specific index from an array when filtering

I'd like to filter an array of numbers and use reduce on them, but I need to exclude a specific index and I can't divide. Is it possible to do this with methods that are part of Foundation in Swift?

I've tried breaking the array into two using prefix & suffix, but there are some edge cases where it blows up w/ an out of bounds exception.

    while currentIndex < nums.count - 2 {
        for _ in nums {
            let prefix = nums.prefix(currentIndex)
            let suffix = nums.suffix(from: currentIndex + 1)
            if prefix.contains(0) || suffix.contains(0) {
                incrementIndex(andAppend: 0)
            }
            let product = Array(prefix + suffix).reduce(1, *)
            incrementIndex(andAppend: product)
        }
    }

Upvotes: 0

Views: 1283

Answers (2)

matt
matt

Reputation: 534925

I'm seeking to figure out how to exclude a specific index

What about this sort of thing?

var nums2 = nums
nums2.remove(at:[currentIndex])
let whatever = nums2.reduce // ...

Where remove(at:) is defined here: https://stackoverflow.com/a/26308410/341994

Upvotes: 1

Keshu R.
Keshu R.

Reputation: 5215

You can use enumerated() to convert a sequence(eg. Arrays) to a sequence of tuples with an integer counter and element paired together

var a = [1,2,3,4,5,6,7]
var c = 1
let value  = a.enumerated().reduce(1) { (_, arg1) -> Int in
    let (index, element) = arg1
    c = index != 2 ? c*element : c
    return c
}
print(value) // prints 1680 i.e. excluding index 2

Upvotes: 2

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