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iosarraysswift
WilburDD
WilburDD

Reputation: 47

Summing columns in a 2D array in Swift

I have a simple 2D array of integers named "round", with 5 elements on the horizontal and a variable number of "rows".

I want to calculate the total for each "column". Here's my code:

var totals = [Int] ()

for column in 0...4 {
    for row in 0...round.count-1 {
        totals[column] = round[row][column] + totals[column]   }
}

I get a Playground "Fatal error: Index out of range"

In trying various options, it appears to be the "totals[column] = " assignment that throws the error, but I cannot determine why?

Upvotes: 0

Views: 220

Answers (1)

finebel
finebel

Reputation: 2355

The problem is totals[column] since totals is an empty array it has no element at the index column.
It's similar to the following attempt:

var arr = [Int]()
arr[0] = 1 // <- fails, because there is no element at index 0

To fix this issue, you can initialize totals with zeros for the number of elements you want to store in the array:

var totals = Array(repeating: 0, count: round[0].count)

Or even simpler (but less dynamic):

var totals = [0, 0, 0, 0, 0]

Upvotes: 1

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