using System;
using System.Globalization;
/*
Program: Print numbers with a thousand separator as spaces in C#.
Architecture notes:
-------------------
- .NET's NumberFormatInfo allows customizing:
* NumberGroupSeparator → " "
* NumberGroupSizes → {3}
- We create a reusable formatter and apply it to all numeric output.
- This avoids repeated allocations and keeps formatting consistent.
Performance notes:
------------------
- Formatting is O(n) in the number of digits.
- NumberFormatInfo is lightweight and safe for repeated use.
- Memory usage is minimal; only small strings are created.
Pitfalls:
---------
- NumberFormatInfo is not thread-safe if modified after creation.
- Negative numbers must preserve the minus sign; .NET handles this automatically.
- Very large numbers (BigInteger) require converting to string first.
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
*/
class ThousandSeparatorSpaces
{
// Reusable formatter with space as thousands separator
private static readonly NumberFormatInfo SpaceFormat = CreateSpaceFormat();
private static NumberFormatInfo CreateSpaceFormat()
{
var nfi = new NumberFormatInfo
{
NumberGroupSeparator = " ",
NumberGroupSizes = new[] { 3 }
};
return nfi;
}
// Format a number using the custom NumberFormatInfo
private static string FormatWithSpaces(long value)
{
try
{
return value.ToString("N0", SpaceFormat);
}
catch (Exception ex)
{
return $"unformatted (error: {ex.Message})";
}
}
static void Main()
{
long[] tests =
{
0,
42,
1234,
987_654_321,
-1_234_567,
1_000_000_000_000_000_000L // 10^18
};
Console.WriteLine("Running test cases:\n");
foreach (var n in tests)
{
Console.WriteLine("Original: " + n);
Console.WriteLine("Formatted: " + FormatWithSpaces(n));
Console.WriteLine();
}
}
}
/*
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
*/
