Programing Puzzles

[JAnderson]

Koroskin Denis wrote:
> On Thu, 07 Aug 2008 10:50:25 +0400, JAnderson <ask at me.com> wrote:
> 
>> Wyverex wrote:
>>> just some fun little programming puzzles I found around online...
>>>    Write a "Hello World" program in 'C' without using a semicolon.
>>> (Note: #include in C doesn't need a semicolon but import does)
>>>    Problem #1 Write a "Hello World" program in D with only a 
>>> semicolon on import statement.
>>>  Problem #2 Test if an int is even or odd without looping or if 
>>> statement (Cant use: do, while, for, foreach, if).
>>>  Problem #3 Write a program without using any loop (if, for, while 
>>> etc) to print numbers from 1 to 100 and 100 to 1;
>>>  Problem #4 Find if the given number is a power of 2.
>>>    Post Solutions to this root, comments to someones solution in that 
>>> thread.
>>
>> These are pretty standard interview questions. Although I don't 
>> personally like to ask these sort of questions because they are often 
>> about knowing a "trick" which you an easily lookup.  The can be fun to 
>> figure out though.
>>
>> Here's another common one:
>>
>> | Write a bitcount for a 32-bit number.
>>
>> And a little more challenging:
>>
>> | Write a bitcount for a 32-bit number that is less then 15 operations 
>> without using a lookup table.
>>
>> | Can you do that in 12 or less?
>>
>> -Joel
> 
> I know the solution for 15 operations, but it is impossible to come up 
> with solution quickly. Besides, it requires 64 bit arithmetic support.

The 12 op solution doesn't require 64-bit.  Your right though to come up 
with something quickly for a question like this is extremely difficult 
when its been worked on for years, unless you "know" it.

-Joel