Friday Programming Quiz [modified]

Rama Krishna Vavilala

In a language of your choice (no PE), implement the following:

string RemoveDuplicates(string csvString) {

}

The function should remove all duplicate values form a string containing comma separated values. RemoveDuplicates("a,b,c,a") => "a,b,c" RemoveDuplicates("a,b,c,a,c,b,c") => "a,b,c" RemoveDuplicates("a,b,c") => "a,b,c" RemoveDuplicates("cat,dog,dog") => "cat,dog" The ideal implementation should have just 1 line of code.

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. -Brian Kernighan

Jon Sagara

Plain English Function Called "Remove Duplicates" with Argument Consisting of Comma Separated Values in a Character String Remove Duplicate Values From The Plain English Function Argument Consisting of Comma Separated Values in a Character String Return The Plain English Function Argument Consisting of Comma Separated Values in a Character String, But With Duplicate Values Removed End Of Plain English Function Called "Remove Duplicates" with Argument Consisting of Comma Separated Values in a Character String Excuse me while I go hurl X|

Jon Sagara When I grow up, I'm changing my name to Joe Kickass! My Site | My Blog | My Articles

Christian Graus

Ah - now I know what PE is.

Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

ToddHileHoffer

In C# string RemoveDuplicates(string csvString) { string[] x = csvString.Split(char.Parse(",")); System.Collections.Specialized.StringCollection c = new System.Collections.Specialized.StringCollection(); foreach (string y in x) { if (!c.Contains(y)) c.Add(y); } string result = ""; foreach (string z in c) { result += z + ","; } return result.Substring(0, result.Length - 1); }

how vital enterprise application are for proactive organizations leveraging collective synergy to think outside the box and formulate their key objectives into a win-win game plan with a quality-driven approach that focuses on empowering key players to drive-up their core competencies and increase expectations with an all-around initiative to drive up the bottom-line. But of course, that's all a "high level" overview of things --thedailywtf 3/21/06

Nish Nishant

/*
Needs VC++ 8 to compile
*/
string DoFunc(string s)
{
set<char> st;
for each(char c in s)
{
st.insert(c);
}
st.erase(st.find(','));
char *arr = new char[2 * st.size()];
int index = 0;
for each(char c in st)
{
arr[index++] = c;
arr[index++] = ',';
}
arr[--index] = 0;
s = arr;
delete[] arr;
return s;
}

Regards, Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
Currently working on C++/CLI in Action for Manning Publications. Also visit the Ultimate Toolbox blog

Gary Wheeler

Looks like COBOL, minus the dashes. Minus. Dashes. :rolleyes:

Software Zen: delete this;

Rama Krishna Vavilala

Well, I should have stated that the values are strings not just single characters.

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. -Brian Kernighan

PIEBALDconsult

What's a line of code?

Chris Losinger

template < typename _Cont > void split(const std::string& str, _Cont& _container, const std::string& delim=",")
{
std::string::size_type lpos = 0;
std::string::size_type pos = str.find_first_of(delim, lpos);
while(lpos != std::string::npos)
{
_container.insert(_container.end(), str.substr(lpos,pos - lpos));

    lpos = ( pos == std::string::npos ) ?  std::string::npos : pos + 1;
    pos = str.find\_first\_of(delim, lpos);
}

}

std::string fn(std::string in)
{
std::string out;
std::set foo;
split(in, foo);

for (std::set::iterator it=foo.begin();it!=foo.end();it++)
{
	if ((\*it).size() > 0)
	{
		out+=(\*it);
		if (std::distance(it, foo.end()) > 1) out+=",";
	}
}
return out;

}

and you can count this as my code from CP entry for the day. why is IE (or CP?) putting that sentence inside the PRE ? it's not. it looked fine in FF2.0. -- modified at 19:14 Friday 3rd November, 2006

image processing | blogging

Daniel Grunwald

This is what LINQ is for: return string.Join(",", csvString.Split(',').Distinct()); Edit: Note that it is also the most efficient solution - it's O(N) because Distinct() internally uses a hash table. The C++ set<> solutions are O(N log N), though probably faster in the real world. And everything running Contains() repeatedly will be O(N²). Not that anyone would store large amounts of data in CSV strings.... Second modification: Sadly, it won't work like that. Distinct() returns IEnumerable, but for some strange reason, Join only works with arrays. So if we don't get a new Join() overload in .NET 3.5, add a .ToArray() extension method call behind the Distinct().

Last modified: 24mins after originally posted --

Daniel Grunwald

char.Parse?? Why that? Haven't you heard of character literals: string.Split(',') ? And concatenating using += is the easiest way to screw up your applications performance. For a list with just a few thousand items, you'll be copying multiple GB of RAM. Remember that every operation on a string creates a complete copy of that string, so the StringBuilder is much better here.

Andy Brummer

:-D Please tell me you just made that up. That isn't an actual example of PE programming, it can't be that would just be absurd.

Using the GridView is like trying to explain to someone else how to move a third person's hands in order to tie your shoelaces for you. -Chris Maunder

Marc Clifton

Daniel Grunwald wrote:

This is what LINQ is for:

Very very cool! Marc

Thyme In The Country

People are just notoriously impossible. --DavidCrow
There's NO excuse for not commenting your code. -- John Simmons / outlaw programmer
People who say that they will refactor their code later to make it "good" don't understand refactoring, nor the art and craft of programming. -- Josh Smith

Rama Krishna Vavilala

Depends on the language (probably it is better to call 1 statement instead of 1 line): Something like this[^]

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. -Brian Kernighan

Jon Sagara

Andy Brummer wrote:

Please tell me you just made that up.

Totally. ;)

Jon Sagara When I grow up, I'm changing my name to Joe Kickass! My Site | My Blog | My Articles

realJSOP

This uses a string parser class I wrote (which is available in both MFC and STL versions here on codeproject. I used methods from memory, so they may not be precise, but this should do what you want. The added benefit is that the CQStringParser class supports quoted sub-strings. :) CString RemoveDuplicates(CString strSource) { CQStringParser parser(strSource, ','); int nCount = parser.GetCount(); CStringArray strUniques; bool bFound = false; for (int i = 1; i <= nCount; i++) { CString strStart = parser.GetField(i); int nUniqueSize = strUniques.GetSize(); for (int j = 0; j < nUniqueSize; j++) { if (strStart.CompareNoCase(strUniques.GetAt(i)) == 0) { bFound = true; break; } } if (!bFound) { strUniques.Add(strStart); } } parser.RemoveAll(); int nUniqueSize = strUniques.GetSize(); for (int j = 0; j < nUniqueSize; j++) { parser.AddField(strUniques.GetAt(j)); } CString strResult = parser.RebuildOriginalString(); return strResult; }

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

amclint

Andy Brummer wrote:

Using the GridView is like trying to explain to someone else how to move a third person's hands in order to tie your shoelaces for you. -Chris Maunder

ROFL, good sig

Stuart Dootson

In Haskell,

import Data.List
removeDuplicates csvStr = nub (map (delete ',') (groupBy (\a b -> b == ',') csvStr))

I had to write the 'split on ,' functionality, which takes most of the declaration (it's this bit map (delete ',') (groupBy (\a b -> b == ',') csvStr)), but Haskell handily has a 'remove duplicates from a list' function, nub. [Edit]Whoops - forgot to reconstruct the string (also, didn't cope with multi-char strings)!

import Data.List
removeDuplicates csvStr = concat $ intersperse "," $ nub $ map (delete ',') (groupBy (\a b -> b /= ',') csvStr)

[/Edit] [Edit 2] And on further investigation of Haskell's libraries, there's a splitRegex function:

import Data.List -- for intersperse, nub
import Text.Regex -- for splitRegex, mkRegex
removeDuplicates csvStr = concat $ intersperse "," $ nub $ splitRegex (mkRegex ",") csvStr

[/Edit 2]

Chris S Kaiser

This just won't ever get old... :laugh::laugh::laugh:

What's in a sig? This statement is false. Build a bridge and get over it. ~ Chris Maunder

PIEBALDconsult

public static string RemoveDuplicates ( string Subject ) { System.Text.StringBuilder result = new System.Text.StringBuilder ( Subject.Length ) ; System.Collections.Specialized.StringCollection dic = new System.Collections.Specialized.StringCollection() ; foreach ( string temp in Subject.Split ( new char[] { ',' } , System.StringSplitOptions.None ) ) { if ( !dic.Contains ( temp ) ) { dic.Add ( temp ) ; result.Append ( temp ) ; result.Append ( "," ) ; } } return ( result.Remove ( result.Length-1 , 1 ).ToString() ) ; }