Finding the lowest NSInteger from NSArray

Question

I am trying to return the lowest number in an array.

Parameter: arrayOfNumbers - An array of NSNumbers.

Return: The lowest number in the array as an NSInteger.

The code I have thus far doesn't give me any errors, but does not pass the unit tests. What am I doing wrong?

- (NSInteger) lowestNumberInArray:(NSArray *)arrayOfNumbers {

    NSNumber* smallest = [arrayOfNumbers valueForKeyPath:@"@min.self"];
    for (NSInteger i = 0; i < arrayOfNumbers.count; i++) {
        if (arrayOfNumbers[i] < smallest) {
            smallest = arrayOfNumbers[i];
        }
    }

    NSInteger smallestValue = [smallest integerValue];
    return smallestValue;

}

This is the unit test:

- (void) testThatLowestNumberIsReturned {
    NSInteger lowestNumber = [self.handler lowestNumberInArray:@[@3, @8, @-4, @0]];
    XCTAssertEqual(lowestNumber, -4, @"Lowest number should be -4.");

    lowestNumber = [self.handler lowestNumberInArray:@[@83, @124, @422, @953, @1004, @9532, @-1000]];
    XCTAssertEqual(lowestNumber, -1000, @"Lowest number should be -1000.");    
}

you are comparing objects with c types, resulting im pointer addresses being compared with an int. — vikingosegundo, Sep 02 '15 at 17:53
Why do you have that for loop at all? You are already getting the min in the first line. — dan, Sep 02 '15 at 17:55
@vikingosegundo got it! thanks! I've been chasing my own tail for a while. LOL — ioskaveen, Sep 02 '15 at 18:04

score 3 · Accepted Answer · answered Sep 02 '15 at 17:55

3

This method

NSNumber* smallest = [arrayOfNumbers valueForKeyPath:@"@min.self"];

will already determine the smallest number in the array, so the loop inside the method is superfluous (on top of being plain wrong, as @vikingosegundo notices).

answered Sep 02 '15 at 17:55

Glorfindel

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Got it thanks! I've been chasing my own tail for awhile. – ioskaveen Sep 02 '15 at 18:05

vikingosegundo · Answer 2 · 2015-09-02T17:59:57.633

you are comparing objects with c types, resulting im pointer addresses being compared with an int.

Beside the fact your smallest is already the smallest, as you used the KVC collection operator @min.self (see Glorfindel answer), the following code shows you correct comparison

if (arrayOfNumbers[i] < smallest)

should be

if ([arrayOfNumbers[i] compare:smallest] == NSOrderingAscending)

or

if ([arrayOfNumbers[i] integerValue] < [smallest integerValue])

Finding the lowest NSInteger from NSArray

2 Answers2