How to split an NSArray into two equal pieces?

Question

I have an NSArray, and I want to split it into two equal pieces (if odd \"count\" then add to the latter new array) - I want to split it \"down the middle\" so to speak.

Answer 1

You also have the option of using -subarrayWithRange: detailed in the NSArray documentation:

NSArray *firstHalfOfArray;
NSArray *secondHalfOfArray;
NSRange someRange;

someRange.location = 0;
someRange.length = [wholeArray count] / 2;

firstHalfOfArray = [wholeArray subarrayWithRange:someRange];

someRange.location = someRange.length;
someRange.length = [wholeArray count] - someRange.length;

secondHalfOfArray = [wholeArray subarrayWithRange:someRange];

This method returns new, autorelease-d arrays.

Answer 2

If you want an extra object on first array (in case total items are odd), use following code modified from Alex's answer:

NSArray *arrayTotal = [NSArray arrayWithObjects:@"A", nil];
//NSArray *arrayTotal = [NSArray arrayWithObjects:@"A", @"B", nil];
//NSArray *arrayTotal = [NSArray arrayWithObjects:@"A", @"B", @"C", nil];
//NSArray *arrayTotal = [NSArray arrayWithObjects:@"A", @"B", @"C", @"D", nil];
//NSArray *arrayTotal = [NSArray arrayWithObjects:@"A", @"B", @"C", @"D", @"E", nil];

NSArray *arrLeft;
NSArray *arrRight;

NSRange range;
range.location = 0;
range.length = ([arrayTotal count] % 2) ? ([arrayTotal count] / 2) + 1 : ([arrayTotal count] / 2);

arrLeft = [arrayTotal subarrayWithRange:range];

range.location = range.length;
range.length = [arrayTotal count] - range.length;

arrRight = [arrayTotal subarrayWithRange:range];

NSLog(@"Objects: %lu", (unsigned long)[arrLeft count]);
NSLog(@"%@", [arrLeft description]);

NSLog(@"Objects: %lu", (unsigned long)[arrRight count]);
NSLog(@"%@", [arrRight description]);

Answer 3

Have you tried adding nil to the end of the -initWithObjects: method?

NSArray *leftArray = [[NSArray alloc] initWithObjects:[testableArray objectsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(????, ????)]], nil];
NSArray *rightArray = [[NSArray alloc] initWithObjects:[testableArray objectsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(????, ????)]], nil];