Shuffle NSMutableArray

Vineesh · July 2012

Iam started to make a simple quiz application in Xcode Viewbased application for iPhone.

I have 50 questions all questions are in the array. I have to select questions random with out repeat questions.

vineeshtp88@gmail.com

Thanks in Advance

the_stig · July 2012

Best way to do that is just generate a random number then access the array item at that particular index.


#include <stdlib.h>

int numberOfItemsInArray = [arrayWithQuestions count]; //find out how many questions you have

int randomNumber = arc4random() % numberOfItemsInArray; //generate a number less that or equal to the number of questions

[arrayWithQuestion objectAtIndex:randomNumber]; //do with this what you will, this will return a random array item

Note: This code is untested.

smithdale87 · July 2012

This does not prevent you from selecting the same question multiple times, though.

djbrooks111 · July 2012

I had wanted to do this as well and discovered how:

randomPhrases is my NSMutableArray. The method shuffles the array and shows the array in the console once it is shuffled.

-(void)shuffleQuestions {
    NSUInteger firstObject = 0;
    for (int i = 0; i < [randomPhrases count]; i++) {
        NSUInteger randomIndex = arc4random() % [randomPhrases count];
        [randomPhrases exchangeObjectAtIndex:firstObject withObjectAtIndex:randomIndex];
        firstObject += 1;
    }
    NSLog(@"Shuffled array:\n\n%@", randomPhrases);
}

the_stig · July 2012

smithdale87 said:
This does not prevent you from selecting the same question multiple times, though.

I need to learn to read the problem better. lol. If it's an NSMutableArray you can just remove that item once you're finished though yeah?

Vineesh · July 2012

the_stig said:
Best way to do that is just generate a random number then access the array item at that particular index.

#include <stdlib.h> int numberOfItemsInArray = [arrayWithQuestions count]; //find out how many questions you have int randomNumber = arc4random() % numberOfItemsInArray; //generate a number less that or equal to the number of questions [arrayWithQuestion objectAtIndex:randomNumber]; //do with this what you will, this will return a random array item

Note: This code is untested.

It is repeating numbers.

djbrooks111 · July 2012

Here is my friendly reminder that I already posted the solution to properly shuffling a NSMutableArray in my above post :)

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