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How to create an array by repeating an item

Swift version: 5.2

Paul Hudson    @twostraws   

If you need to create an array of a specific size holding some default values, Swift has a built-in initializer called repeating:count:. You tell it what to repeat, and how often, and Swift will generate an array of that size.

For example, this creates an array of 100 items, all containing 0:

let numbers1 = [Int](repeating: 0, count: 100)

You can even use this initializer to create multi-dimensional arrays, for example an array of arrays of numbers:

let numbers2 = [[Int]](repeating: [Int](repeating: 0, count: 100), count: 100)

You can use this when creating a game board: mark all rows and columns as being 0 for a 100x100 board, then fill in squares as the game proceeds.

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