Consolidating overlapping sets from an array of sets

Question

I have an array with each entry containing a minimum and a maximum value for a bunch of sets such as the one below:

Array
(

    [0] => Array
        (
            [0] => 1200
            [1] => 2400
        )

    [1] => Array
        (
            [0] => 1400
            [1] => 3800
        )

    [2] => Array
        (
            [0] => 2700
            [1] => 4200
        )
    [3] => Array
        (
            [0] => 5900
            [1] => 6400
        )

)

For each index, the 0 index is the minimum value and the 1 index is the maximum value for that particular set. I need to create a javascript or php function to consolidate this array so that the sets that overlap are turned into one. So, the above array would turn into the following:

Array
(

    [0] => Array
        (
            [0] => 1200
            [1] => 4200
        )
    [1] => Array
        (
            [0] => 5900
            [1] => 6400
        )

)

As you can see, from the first array indicies 0, 1, and 2 were consolidated into index 0 for the second array. Index 3 from the first array did not overlap with any other set so that became index 1 in the second array.

The original array itself will contain around 70 to 80 sets and the min and max values can get as high as 9999999999 so iterating through a number line in a n, n+1, n+2 manner is not feasible.

Any ideas?

UPDATE + SOLUTION

As stated in the comment below, this is indeed a repost (didn't see the other post). The link for the solution is at the link below:

Merging overlapping ranges in PHP arrays?

Looks like a duplicate of stackoverflow.com/questions/3630500/… — Matthew
– Matthew, Commented Sep 17, 2010 at 3:48
Sorry for the late reply, got caught up with some projects. Indeed, it does look like a repost.. didn't see that post when I was looking for it :/ Thank you konforce. Thank you as well Andrew Cooper. — user396404
– user396404, Commented Sep 21, 2010 at 9:40

Andrew Cooper · Accepted Answer · 2010-09-17 03:29:30Z

0

Assuming the sets are ordered by lower bound, as in the example, how about something like this?

var newIndex = 0;
var newSetArray[newIndex][0] = setArray[0][0];
for (i = 1; i < setArray.length; i++) {
    if (setArray[i-1][1] < setArray[i][0]) {
        newSetArray[newIndex][1] = setArray[i-1][1];
        newSetArray[++newIndex][0] = setArray[i][0];
    }
}
newSetArray[newIndex][1] = setArray[setArray.length-1][1];

The syntax might need some tweaks, but I think this should work.

answered Sep 17, 2010 at 3:29

Andrew Cooper

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