Help me solve this puzzle?

IamtheWalrus

I have a puzzle to solve where I have to write a small Java program that takes s input a number and outputs that word in numeric.

E.g. 1 = one, 1001 = one thousand and one.

I have written the program but have found a bug in it. The program is sometimes dropping the word 'and'.
If I enter 1001, I get one thousand one (as opposed to one thousand and one). Same as 10001, I get ten thousand one ('and' missing again).

If I enter 1101, I correctly get one thousand one hundred and one. This is because there is 1 as the second digit.

Can anyone tell me how to resolve this issue? If spent hours at it and am stuck.

final private static String[] units = {"zero","one","two","three","four",
		"five","six","seven","eight","nine","ten",
		"eleven","twelve","thirteen","fourteen","fifteen",
		"sixteen","seventeen","eighteen","nineteen"};
	
	final private static String[] tens = {"","","twenty","thirty","forty","fifty",
		"sixty","seventy","eighty","ninety"};

	public String convert(Integer num){
		
		if( num < 20) return units[num];
		if( num < 100) return tens[num/10] + ((num % 10 > 0)? " " + convert(num % 10):"");
		if( num < 1000) return units[num/100] + " hundred" + ((num % 100 > 0)? " and " + convert(num % 100):"");
		if( num < 100000) return convert(num / 1000) + " thousand" + ((num % 1000 > 0)? " " + convert(num % 1000):"") ;
		return convert(num / 1000000) + " million" + ((num % 1000000 > 0)? " " + convert(num % 1000000):"") ;
	}

Slashman X

if( num < 1000) return units[num/100] + " hundred" + ((num % 100 > 0)? " and " + convert(num % 100):"");

Change to >=

PrzemoF

For 1001 only this line is used:

if( num < 100000) return convert(num / 1000) + " thousand" + ((num % 1000 > 0)? " " + convert(num % 1000):"") ;

it generates "one thousand" and then calls
convert with number 1 which generates "one" so you get "one thousand one".

The "and" part is generated only for numbers between 101 and 999 and that line is never called for numbers like 1001 or 10001.

I'd suggest to make a flowchart to understand how your code works.

IamtheWalrus

Slashman X wrote: »

Change to >=

That made no difference.

IamtheWalrus

PrzemoF wrote: »

it generates "one thousand" and then calls
convert with number 1 which generates "one" so you get "one thousand one".

The "and" part is generated only for numbers between 101 and 999 and that line is never called for numbers like 1001 or 10001.

I had noticed that and that is the bit I cannot fix.

DonkeyStyle \o/

On the thousand and million lines, check if num % is going to be less than 100 before you convert() it, if so, add " and ", if not don't.

Also change your 4th 'if' to check for < 1 million rather than <100k, because your default case won't handle the hundreds of thousands.

IamtheWalrus

DonkeyStyle \o/ wrote: »

On the thousand and million lines, check if num % is going to be less than 100 before you convert() it, if so, add " and ", if not don't.

Also change your 4th 'if' to check for < 1 million rather than <100k, because your default case won't handle the hundreds of thousands.

It's working. Can't thank you enough Donkey.

Slashman X

IamtheWalrus wrote: »

That made no difference.

Ah my bad, read the code wrong. Stupid scrolling code boxes

bpmurray

Try

if (num < 100000)
   return convert(num / 1000) + " thousand"
		+ ((num % 1000 > 0) ? ((num % 100 > 0) ? " and " : " ") + convert(num % 1000) : "");