Solution to the Coin Change Problem in Objective-C

CDRCoinChangeValidator.m

// just the method body; complete the rest of the class declaration yourself.

+ (BOOL)isValidAmount:(int)target forDenominations:(NSArray *)denominations
{
    if(denominations.count == 0)
        return NO;

    if(target < 0)
        return NO;

    if(target == 0)
        return YES;

    NSMutableArray *results = [NSMutableArray arrayWithCapacity:target + 1];

    for(int i = 0; i < target+1; i++)
    {
        [results insertObject:[NSNumbernumberWithInt:0] atIndex:i];
    }

    [results replaceObjectAtIndex:0withObject:[NSNumbernumberWithInt:1]];

    for(int i = 0; i < denominations.count; i++)
    {
        for(int j = [denominations[i] intValue]; j <= target; j++)
        {
            int difference = j - [denominations[i] intValue];

            [results replaceObjectAtIndex:j withObject:[NSNumber numberWithInt:[results[j] intValue] + [results[difference] intValue]]];

            if(j == target && [results[j] intValue] > 0)
                return YES;
        }
    }    

    returnNO;
}