C++ Coding Challenges

[Killerapathy]

I have been learning C++ for over a year now and I would like to ask the community for some C++ coding challenges or puzzles. My professors have given me ones such as ...

int strlen(char * sz)
{

}
note: solution only took 3 lines using (recursion)

OR

"Write a C function that multiplies an input integer by 5 and returns the result. The function must not use the multiplication operator. Optimize for speed."
I believe this one actually goes into the bits.


Anyways, I wonder if you could share some of yours in hopes of challenging others.

[ndimucci]

http://www.codechef.com/

Up top you'll see a "Practice" tab which will provide problems to solve. There are even competitions in which you can enter. It's a great site.

[dmmik]

Here is a whiteboard C coding question I was asked at an actual game company interview. Complete this function:

bool IsPalendrome(char* str)
{

}

[yaustar]

Try the demo test on http://codility.com/

[ndimucci]

Originally Posted by yaustar

Try the demo test on http://codility.com/

Awesome site. Annoying that you have to pay for it, but probably worth it to better prepare for interviews and such.

[yaustar]

The free demo test itself is usually pretty decent. Codility is for the hiring managers to sends tests out rather then preparing for interviews.

[Tonsko]

Originally Posted by dmmik

Here is a whiteboard C coding question I was asked at an actual game company interview. Complete this function:

bool IsPalendrome(char* str)
{

}

Apologies for thread resurrection.

I saw this last night while browsing, and it's a nice little problem, if not especially taxing. As a novice, I originally thought it would be best to break it down into an array and do something complicated such as reversing the order of the array and then comparing them. But there is no need - after further reading, having seen the string tools available. Once I was thinking along those lines, it took about 20 mins.

So here's a solution (in python rather than C) - anyone got any optimisation tips?

#!/usr/bin/python

def isPalindrome(string):
    length = len(string)
    #print length
    
    i=0
    j=length
    
    while j > 0:
    	if string[i] == string[j-1]:
    		#print string[i],string[j-1]
    		i=i+1
    		j=j-1
    	else:
		print 'Not a palindrome'
		break
    	
    	if j == 0:
    		print 'Word is a palindrome'
    	else:
    		pass
    		
input = raw_input()
isPalindrome(input)

The mild advantage of this is that it's not typed, so works equally well with palindromic numbers. For the c problem, I guess you'd have to put in some type checking to sanitise the input before doing anything.

[Protector one]

As for "optimizations", instead of, "while j > 0", you could use, "while j > length*.5", since you've already checked the first n/2 letters of the word. :P
(I might be off by one. Sorry for that, if so.)

[yaustar]

Originally Posted by cuxxie

int strlen(char * sz)
{
if((*sz)!='\0') return (strlen(++sz)+1);
else return 0;
}

string length counter... 2 lines..

Technically, that is 4 logical lines of code. Otherwise we could do this and call it one line of code.

int strlen(char * sz)
{
	if((*sz)!='\0') return (strlen(++sz)+1); else return 0;
}

[cowsonparade]

Well, depends on the definition of optimization:

def isPalindrome(string):
    #More of a C-style optimization for memory usage
    for i in range(len(string)/2): #rounds down, which is OK because middle letter can be ignored
        if string[i] != string[-i-1]:
            return False
    else: return True

def isPalindrome(string):
    #Optimizes developer time XD
    return string == reverse(string)

I'm a big fan of http://projecteuler.net/ for programming puzzles. A friend of mine would try to solve each one with 1 line.

Originally Posted by Tonsko

Apologies for thread resurrection.

I saw this last night while browsing, and it's a nice little problem, if not especially taxing. As a novice, I originally thought it would be best to break it down into an array and do something complicated such as reversing the order of the array and then comparing them. But there is no need - after further reading, having seen the string tools available. Once I was thinking along those lines, it took about 20 mins.

So here's a solution (in python rather than C) - anyone got any optimisation tips?

#!/usr/bin/python

def isPalindrome(string):
    length = len(string)
    #print length
    
    i=0
    j=length
    
    while j > 0:
    	if string[i] == string[j-1]:
    		#print string[i],string[j-1]
    		i=i+1
    		j=j-1
    	else:
		print 'Not a palindrome'
		break
    	
    	if j == 0:
    		print 'Word is a palindrome'
    	else:
    		pass
    		
input = raw_input()
isPalindrome(input)

The mild advantage of this is that it's not typed, so works equally well with palindromic numbers. For the c problem, I guess you'd have to put in some type checking to sanitise the input before doing anything.