DaniWeb Forum Index > Software Development > C++

Help needed filling array with unique random numbers

« First

•

Join Date: Dec 2008

Posts: 1

Reputation: kitf84 is an unknown quantity at this point

Solved Threads: 0

kitf84

Offline

Newbie Poster

Re: Help needed filling array with unique random numbers

#31

Dec 1st, 2008

•

Originally Posted by bling_bling_vr6

Hello, I need some help filling an array with UNIQUE random numbers. So far I've figured out how to fill an array with random numbers, that's easy, but I'm stuck on how to avoid filling it with duplicate values. I'm assuming that i'll have to use either a linear or binary search function while filling the array, but my attempts so far have failed. Anyone got any idea what i'm doing wrong? Here's my terrible code so far...any help would dearly be appreciated.

I recently had a situation where I had to choose 10 random questions out of a bank of 30. The questions should be unique. There are probably more efficient ways of doing this and there is the potential for an infinite loop (or at least a really long one)

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
//Pick 10 unique random questions out of a bank of 30 
int currentRandInt;
questionNumbers[0] = getRandInt(0,29); //First one's free
for (int i = 1; i < 10; i++)
{
        currentRandInt = getRandInt(0,29); //Get a rand int
 
        //Check this rand int against all previous stored values
        for int (j = 0; j < i; j++)
        {
             if(currentRandInt == questionNumbers[i])
    	     {
    	        //If we have a match, get a new rand int and begin again
    	        currentRandInt = getRandInt(0,29);
      	        j = 0; //Here's where the potential for infinite loop is introduced
     	     }
	 }
	 //If this is a unique rand int then keep it and proceed to to the next value
        questionNumbers[i] = currentRandInt;
}
//Pick 10 unique random questions out of a bank of 30 
int currentRandInt;
questionNumbers[0] = getRandInt(0,29); //First one's free
for (int i = 1; i < 10; i++)
{
        currentRandInt = getRandInt(0,29); //Get a rand int
    
        //Check this rand int against all previous stored values
        for int (j = 0; j < i; j++)
        {
             if(currentRandInt == questionNumbers[i])
    	     {
    	        //If we have a match, get a new rand int and begin again
    	        currentRandInt = getRandInt(0,29);
      	        j = 0; //Here's where the potential for infinite loop is introduced
     	     }
	 }
	 //If this is a unique rand int then keep it and proceed to to the next value
        questionNumbers[i] = currentRandInt;
}