CODEWITHSUNDEEP
iphonexcoderandom
iUser
iUser

Reputation: 1075

Random numbers without repetition

I am making Quiz app in which i want to generate random numbers without repetition.
I have searched many things and got the idea but i think i am doing something wrong that's why not getting correct output.

Here is the code that i used. 

-(int)generater{

NSMutableArray *temp;
srand([[NSDate date] timeIntervalSince1970]);
r = 1 + (arc4random() % 11);

if ([temp count] ==0) {

    [temp addObject:[NSNumber numberWithInteger:questionnumber]];
    return r;

}
if ([temp count] >= 1 ){

    if (![temp containsObject:[NSNumber numberWithInteger:questionnumber]]) {

        return r;

    }
    else{

        int next=[self generater];
        return next;
    }
}
return r;
}

For next Question,

-(void)askQuestion{

[self generater];

questionnumber = r;

NSInteger row = 0;
if(questionnumber == 1)
{
    row = questionnumber - 1;
}
else
{
    row = ((questionnumber - 1) * 11);
}

Can any one suggest me where i am wrong ?

Upvotes: 3

Views: 2615

Answers (6)

Eimantas Kudarauskas
Eimantas Kudarauskas

Reputation: 73

Random number between two numbers method:

- (int)randomFromSmallest: (int) smallest toLargest: (int) largest
{
    int random = smallest + arc4random() % (largest + 1 - smallest);
    return random;
}

And that's how I filling an array of non-repeating numbers:

NSMutableArray *randNrArray = [[NSMutableArray alloc] init];

while ([randNrArray count] < 25)
{
    int rndNumber = [self randomFromSmallest:0 toLargest:25 - 1];

    if (![randNrArray containsObject:[NSNumber numberWithInt:rndNumber]])
    {
        [randNrArray addObject:[NSNumber numberWithInt:rndNumber]];
        //NSLog(@"___ %d ___", rndNumber);
    }
}

I hope this helps.

Upvotes: 1

user1882026
user1882026

Reputation: 

    arryRandomNumber=[[NSMutableArray alloc]init];
    while (arryRandomNumber.count<12) {
    NSInteger randomNumber=1+arc4random()%12;
    if (![arryRandomNumber containsObject:[NSString stringWithFormat:@"%d",randomNumber]])       {
          [arryRandomNumber addObject:[NSString stringWithFormat:@"%d",randomNumber]];
     }
         continue;
    }
     NSLog(@"%@",arryRandomNumber);

Upvotes: 4

Mrunal
Mrunal

Reputation: 14128

Hope this code will help you...

Here limit should be set by your requirement.

Benefit of this code is it won't repeat the same random number which is already been got. (No repetitive numbers)

srand(time(NULL));

int randomIndex = rand() % limit;

[reportIDTextField setText:[NSString stringWithFormat:@"%i", randomIndex]];

Enjoy coding :)

Upvotes: 1

andyroberts
andyroberts

Reputation: 3518

Surely the best approach is to put all the questions (or question numbers) sequentially into an array, and then shuffle them.

See What's the Best Way to Shuffle an NSMutableArray?

Some additional guidance (NB all code written in the browser and not actually compiled and tested; but should still get the gist):

1) Set up an ivar NSMutableArray *randomQuestionNumbers. Initialise the contents of the array with the number of questions, so if you have 5 questions put the numbers 1-5 in. To do it manually it would be:

randomQuestionNumbers = [NSMutableArray arrayWithObjects:[NSNumber numberWithInt:1], [NSNumber numberWithInt:2], [NSNumber numberWithInt:3], [NSNumber numberWithInt:4], [NSNumber numberWithInt:5], nil];

2) After that, you need to shuffle, by using one of the methods given in the link above. That will transform [1,2,3,4,5] -> [4,1,5,3,2] for example 3) So now create your method to get the next question number:

- (NSInteger) nextQuestionNumber {

  NSInteger nextQuestionNumber = -1;
  if ([randomQuestionNumbers count] > 0) {
      nextQuestionNumber = (NSInteger) [randomQuestionNumbers objectAtIndex:0];
      [randomQuestionNumbers removeObjectAtIndex:0];
  }
  return nextQuestionNumber;
}

What's happening here is we retrieve the first int in the array. Then we remove that element from the array. Finally, we return the int, e.g., 4. The next time the method is called, there is one fewer element, and the first element is the int 1, and so on. I'm rather crudely using -1 to show when the array is empty, but to be honest you should be able to ensure you don't call the method more times that necessary.

Upvotes: 3

Julien
Julien

Reputation: 155

Maybe : r = [self generater];

questionnumber = r;

Upvotes: 0

Cyrille
Cyrille

Reputation: 25144

Put all your question numbers in a NSMutableArray (1, 2, 3, 4, 5, 6, 7, 8), then perform a number of permutations on this array.

I use this approach to scramble a numeric keypad:

// Randomize keys: exchange two random keys, ten times.
for (int i = 0; i < 10; i++)
{
    int a = 0, b = 0;
    while (a == b)
    {
        a = arc4random() % 10;
        b = arc4random() % 10;
    }
    UIButton *btnA = (UIButton *)[_scrambledKeypad viewWithTag:a + 10];
    UIButton *btnB = (UIButton *)[_scrambledKeypad viewWithTag:b + 10];
    CGRect frame = btnA.frame;
    btnA.frame = btnB.frame;
    btnB.frame = frame;
}

Upvotes: 0

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