Selecting random numbers iphone sdk

Question

I want to select 10 random numbers from 1 to 35.

I am trying to do the following, but I get some repeated numbers

int totalNumberCnt = 1;
while (totalNumberCnt < 11) {
    int randomNumber1 =  1 + arc4random() % 35;
    NSString *numberString = [NSString stringWithFormat: @"%d",randomNumber1];
    NSLog(numberString);
    [firstNumber addObject:numberString];
    [secondNumber addObject:numberString];
    totalNumberCnt++;
}

Thank you for your help.

possible duplicate of http://stackoverflow.com/questions/1617630/non-repeating-random-numbers — kennytm, Apr 28 '10 at 19:58
If you want a 35 unordered but unique numbers, you should use an NSSet. — TechZen, Apr 28 '10 at 23:24

score 2 · Answer 1 · answered Apr 28 '10 at 19:55

2

Repeated numbers are to be expected; it is random after all, and any random sample will contain repeats.

answered Apr 28 '10 at 19:55

Randolpho

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score 0 · Answer 2 · answered Apr 29 '10 at 04:19

int unique = 0;
int numbers[35];

for (int i = 0; i < 35; i++) {
    numbers[i] = 0;
}

while (unique < 10) {
    int x = arc4random() % 35;
    if (numbers[x] == 0) {
        numbers[x] = 1;
        ++unique;
    }
}

for (int i = 0; i < 35; i++) {
    if (numbers[i] == 1) {
        NSString *str = [NSString stringWithFormat: @"%d", i];
        NSLog(@"%@", str);
    }
}

Selecting random numbers iphone sdk

2 Answers2