Round Integer Numbers in Swift

Question

I would like to round the integer number to the nearest hundredth for currency purposes, How is it possible in Swift?

Example: 1397968 becomes 1397900

Answer 1

If you want to round down to a multiple of 100 then you can do that with (as @vadian said in a comment):

let amount = 1397968
let rounded = amount/100 * 100
print(rounded) // 1397900

This works because integer division truncates the result towards zero: amount/100 evaluates to 13979, and multiplying by 100 again gives 1397900.

But you asked for the nearest multiple of 100 for a given integer, and that can be done with a small modification:

let amount = 1397968
let rounded = (amount + 50)/100 * 100
print(rounded) // 1398000

for nonnegative integers. If you have both positive and negative values then @shallowThought's answer is probably the easiest way to go. But it can be done with pure integer arithmetic as well (using the approach from Make Int round off to nearest value):

func roundToHundreds(_ value: Int) -> Int {
    return value/100 * 100 + (value % 100)/50 * 100
}

roundToHundreds(123) // 100
roundToHundreds(188) // 200

roundToHundreds(-123) // -100
roundToHundreds(-188) // -200

This works for the full range of Int:

roundToHundreds(Int.max) // 9223372036854775800
roundToHundreds(Int.min) // -9223372036854775800

Answer 2

let value = 1397968
let rounded = Int(round(Double(value) / 100) * 100)
print(rounded)

-> 1398000