Code Crash!!!

Hi,
I've written a code which replaces characters in a string with their respective URLEncode (i.e a " " will be replaced by "+" etc..).
However the code crashes at execution.
Please help!!
Here's the code extract;
Code:
--------------------------------------------------------------------------------
for(j=0;j<one.length();j++)
{

indxD = one.find_first_of ( " " , 0 );
one.replace(indxD,1,"%2B",3);
}
---------------------------------------------------------------------------------

Thank You In Anticipation,
John

Why this was doing on the contest board is beyond me!

MOVED!

uhhmm...maybe you should paste some more code?
It's kinda hard to tell what goes wrong from what you've shown us...

/btq

To have a stab at it;

Code:

#include <iostream>
#include <string>


int main(){

	using std::cout;
	using std::endl;
	using std::string;

	string one("Hello World This Is Encoded");//string to encode
	const string rep("%2B");//replacement token		   
	string::size_type indxD = 0;//return of find...	
				
	std::cout << "Unencoded " << one << std::endl;

	while(1){
		indxD = one.find_first_of (' ',0);//find a char....
		if(indxD == string::npos)break;//if -1 then end (not found!)
		else one.replace(indxD,1,rep.c_str(),rep.length());//replace with token
	}

	std::cout << "Encoded " << one << std::endl;
	

}

I don't think there is something wrong with the loop, maybe it crashes from something else.