Sort multi dimensional array based on sum of internal arrays in objective c

Question

Let's say I have a multi-dimensional array like this:

(
    (2, 2, 1),
    (0, 1, 2),
    (0, 1, 1),
    (0, 0, 1),
    (0, 0, 2),
    (0, 1, 3),
    (0, 1, 0),
    (0, 0, 1),
    (0, 0, 1),
    (1, 3, 3)
)

Now I need to sort this array in descending order of the internal array's sum.

I tried by adding this array and another array of the sum values in a dictionary, but it doesn't work if the sum contains similar numbers.

i.e, I want the result to be:

(1, 3, 3),
(2, 2, 1),
(0, 1, 3),
(0, 1, 2),
(0, 1, 1),
(0, 0, 2),
(0, 0, 1),
(0, 0, 1),
(0, 1, 0)

Any help would be appreciated!

Tj3n · Answer 1 · 2016-03-29T07:59:41.773

3

Fonix's answer is cool, but it's Swift, In Obj-C then do like this:

NSArray *numArray = @[@[@1,@1,@1], @[@0,@0,@0], @[@2,@2,@2], @[@0,@1,@2]];

NSArray *sortedArray;
sortedArray = [numArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
        NSNumber *first = [(NSArray *)a valueForKeyPath:@"@sum.self"];
        NSNumber *second = [(NSArray *)b valueForKeyPath:@"@sum.self"];
        return [first compare:second];
    }];

NSLog(@"sorted %@",sortedArray);

edited Mar 29 '16 at 07:59

answered Mar 29 '16 at 07:56

Tj3n

9,837
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oops completely missed the objective-c part, doh – Fonix Mar 29 '16 at 07:57
1

:D other ppl can search for it in the future so it's still worth keep – Tj3n Mar 29 '16 at 07:58
1

thanks for the effort, but the KVC answer by @Amin Negm-Awas is comparatively easier. – Rajesh S Mar 29 '16 at 09:03

Fonix · Answer 2 · 2016-03-29T08:03:23.223

2

something like this should work

let multiDimenArray = [[0,1,2],[2,3,4],[1,2,3]]

let sorted = multiDimenArray.sort { a, b -> Bool in

    let aR = a.reduce(0, combine:+) //sums the numbers inside a
    let bR = b.reduce(0, combine:+)

    return aR > bR //swap direction of > if you want ascending or descending
}

print(sorted);

prints

[[2, 3, 4], [1, 2, 3], [0, 1, 2]]

edit:

doh, brain forgot that it should be in objective-c

edited Mar 29 '16 at 08:03

answered Mar 29 '16 at 07:47

Fonix

11,447
3
45
74

Worth noting you can just pass the `+` operator into the `combine:` argument of `reduce`, as Swift treats it as a function. – Hamish Mar 29 '16 at 08:01

score 1 · Accepted Answer · answered Mar 29 '16 at 08:01

You can do that with key-value coding:

NSArray *array = …; // Whatever you have

NSSortDescriptor *sorter = [NSSortDescriptor sortDescriptorWithKey:@"@sum.self" ascending:NO]; // @sum is an aggregate
NSArray *sorted = [array sortedArrayUsingDescriptors:@[sorter]]);

Sort multi dimensional array based on sum of internal arrays in objective c

3 Answers3