How to check is a value already exist in NSMutableArray?

Question

I'm generating random number and adding it to array. But I don't want duplicates to be there. How do I check if the value already exists in array? Thank you!

int lowerBound = 0;
int long upperBound = numberOfQuestions;
int randomQuestionNumber = lowerBound + arc4random() % (upperBound - lowerBound);
[_randomQuestionNumberArray addObject:[NSDecimalNumber numberWithInt:randomQuestionNumber]];

Paul.s · Accepted Answer · 2014-03-08T14:46:18.280

4

Sounds like a perfect use case for an NSMutableOrderedSet If ordering is not important then NSMutableSet is your best bet

You should also be using arc4random_uniform instead of arc4random % to reduce modulo bias

edited Mar 08 '14 at 14:46

answered Mar 08 '14 at 14:40

Paul.s

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score 2 · Answer 2 · edited May 23 '17 at 10:26

2

The most common approach is simply to fill the array with all possible values and then shuffle the array. See What's the Best Way to Shuffle an NSMutableArray?

edited May 23 '17 at 10:26

Community

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answered Mar 08 '14 at 14:45

user3386109

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score 1 · Answer 3 · answered Mar 08 '14 at 14:43

1

You can use

BOOl isFound = [_randomQuestionNumberArray containsObject:object];

answered Mar 08 '14 at 14:43

Hossam Ghareeb

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score 0 · Answer 4 · answered Mar 08 '14 at 14:46

int lowerBound = 0;
int long upperBound = numberOfQuestions;
int randomQuestionNumber = lowerBound + arc4random() % (upperBound - lowerBound);
NSDecimalNumber *currentNumber = [NSDecimalNumber numberWithInt:randomQuestionNumber];
if (![_randomQuestionNumberArray containsObject:num]) {
    [_randomQuestionNumberArray addObject:num];
}

How to check is a value already exist in NSMutableArray?

4 Answers4