import Foundation
/*
Program: Print numbers with a thousand separator as spaces in Swift.
Architecture notes:
-------------------
- Swift uses Foundation's NumberFormatter for numeric formatting.
- NumberFormatter allows customizing:
* grouping separator (thousands separator)
* grouping size
* number style
- We configure NumberFormatter to use a space (' ') as the separator.
- The formatter is reused for all numbers to avoid repeated allocations.
Performance notes:
------------------
- Formatting is O(n) in the number of digits.
- NumberFormatter is efficient and optimized in Foundation.
- Memory usage is minimal; only small strings are created.
Pitfalls:
---------
- NumberFormatter is not thread-safe if modified after creation.
- Negative numbers must preserve the minus sign; NumberFormatter handles this.
- Very large integers (beyond Int64) require using Decimal or BigInt libraries.
Security notes:
---------------
- No external input parsing; safe for demonstration.
- Avoid printing sensitive values in real systems.
Tests:
------
- Positive numbers
- Negative numbers
- Zero
- Very large integers
*/
// Create a reusable formatter with space as thousands separator
let spaceFormatter: NumberFormatter = {
let formatter = NumberFormatter()
formatter.numberStyle = .decimal
formatter.groupingSeparator = " "
formatter.groupingSize = 3
formatter.maximumFractionDigits = 0
return formatter
}()
// Format an integer using the custom NumberFormatter
func formatWithSpaces(_ value: Int64) -> String {
if let formatted = spaceFormatter.string(from: NSNumber(value: value)) {
return formatted
}
return "unformatted (error)"
}
func main() {
let tests: [Int64] = [
0,
42,
1234,
987_654_321,
-1_234_567,
1_000_000_000_000_000_000 // 10^18
]
print("Running test cases:\n")
for n in tests {
print("Original: \(n)")
print("Formatted: \(formatWithSpaces(n))")
print()
}
}
main()
/*
run:
Running test cases:
Original: 0
Formatted: 0
Original: 42
Formatted: 42
Original: 1234
Formatted: 1 234
Original: 987654321
Formatted: 987 654 321
Original: -1234567
Formatted: -1 234 567
Original: 1000000000000000000
Formatted: 1 000 000 000 000 000 000
*/
