如何检查NSMutableArray中是否已经存在一个值？

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]];

Answer 1

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

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

Answer 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?

Answer 3

您可以使用

BOOl isFound = [_randomQuestionNumberArray containsObject:object];

Answer 4

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];
}