Need to sort 3 arrays by one key array

Question

I am trying to get 3 arrays sorted by one key array in objective c for the iphone, here is a example to help out...

Array 1      Array 2      Array 3     Array 4
1            15           21          7
3            12           8           9
6            7            8           0 
2            3            4           8

When sorted i want this to look like

Array 1      Array 2      Array 3     Array 4
1            15           21          7
2            3            4           8
3            12           8           9
6            7            8           0 

So array 2,3,4 are moving with Array 1 when sorted.

Currently i am using a bubble sort to do this but it lags so bad that it crashes by app. The code i am using to do this is

int flag = 0;
int i = 0;
int temp = 0;
do 
{
    flag=1;
    for(i = 0; i < distancenumber; i++)
    {
        if(distance[i] > distance[i+1])
        {
            temp = distance[i];
            distance[i]=distance[i + 1];
            distance[i + 1]=temp;

            temp = FlowerarrayNumber[i];
            FlowerarrayNumber[i] = FlowerarrayNumber[i+1];
            FlowerarrayNumber[i + 1] = temp;

            temp = BeearrayNumber[i];
            BeearrayNumber[i] = BeearrayNumber[i + 1];
            BeearrayNumber[i + 1] = temp;
            flag=0;
        }
    }

}while (flag==0);

where distance number is the amount of elements in all of the arrays, distance is array 1 or my key array.

and the other 2 are getting sorted.

If anyone can help me get a merge sort(or something faster, it is running on a iPhone so it needs to be quick and light) to do this that would be great i cannot figure out how the recursion works in this method and so having a hard time to get the code to work. Any help would be greatly appreciated

Answer 1

Can't you simply structure your array to have A array that each item holds a array ?

Then simply sort your array based on the first item of the array it holds, or have a simple struct that holds an item and also the array.

Answer 2

This is not a objective c specific question. This is an algorithmic question.

1. First sort the first array.
2. Loop through the first array and find the index for each number.
3. Then retrieve the value in second array corresponding to the index in step 2.
4. construct a new array that holds the results in step 3.
5. Repeat step 2,3,4 for the other arrays as well.

Answer 3

I'm just thinking out loud here, but if all of your arrays correspond with each other (that is, BeearrayNumber[x] corresponds with FlowerarrayNumber[x], which corresponds with distance[x]), then you could consider using an array of structures rather than independent arrays. For example:

typedef struct
{
    int flowerNumber;
    int beeNumber;
    float distance;
} BeeFlowerData;

#define MAX_BEE_FLOWER_DATA (100)

BeeFlowerData allBeeFlowers[MAX_BEE_FLOWER_DATA];

Then, you can sort using POSIX qsort:

int BeeFlowerComparator(const void *l, const void *r)
{
    const BeeFlowerData *left = l;
    const BeeFlowerData *right = r;

    if (left->distance > right->distance)
        return 1;
    else if (left->distance < right->distance)
        return -1;
    else 
        return 0;
}


// somewhere in your class:
- (void) sort
{
    qsort (allBeeFlowers, MAX_BEE_FLOWER_DATA, sizeof(BeeFlowerData), BeeFlowerComparator);
}

Answer 4

``Sorry cannot get logged back into my account but for your answer dreamlax. in the BeeFlowerComparator method can you explain this to me. You have paramaters for this method but when you call it in the sort method it does not pass anything is it auto passed? Also in that method

const BeeFlowerData *left = l; const BeeFlowerData *right = r;

if (left->distance > right->distance) 
    return 1; 
else if (left->distance < right->distance) 
    return -1; 
else  
    return 0; 

what does this code do? I cannot figure out what the "->" operand code does.

Answer 5

I can't believe no one has suggested wrapping them in an object yet. It's fairly trivial:

//MyObject.h
@interface MyObject : NSObject {
  int a;
  int b;
  int c;
  int d;
}
@property int a;
@property int b;
@property int c;
@property int d;
@end

//MyObject.m
@implementation MyObject
@synthesize a, b, c, d;
@end

//Elsewhere:

MyObject * m = [[MyObject alloc] init];
[m setA:1];
[m setB:15];
[m setC:21];
[m setD:7];

[myMutableArray addObject:m];
[m release];
//... do that for the rest of the sets of numbers

NSSortDescriptor * sortByA = [NSSortDescriptor sortDescriptorWithKey:@"a" ascending:YES];
[myMutableArray sortUsingDescriptors:[NSArray arrayWithObject:sortByA]];

When you do that, you'll have one array, but the objects in that array will be sorted by their "a" value in ascending order.