Question

So I got a problem that I can’t wrap my mind around.

I’m creating a shopping list that is divided into ten categories of various lengths. (All of the items come from a database). I got it to work when using a single column, but I have to divide the list into four columns. The code should decide which categories should go where so that the four columns have the most equal number of items possible.

This is what the list will look like when the code is working.

Out of these ten categories, four of them have a specific category they belong to.

The way I’ve approached this is to count the total number of items and divide it by four to compute the average number of items per column. I put the four special categories in their respective column and kept track of how many items were now in each column.

Now I still have six columns remaining of various sizes. What is the best approach to put them in the column that would fit best? Since some categories are much larger than others, some columns could potentially have three or four categories.

UPDATE: Right after I posted this I came to the realization that I should find the column with the least items and add the largest category to it. This seems like it will work. And it looks like Dave is suggesting the same!

Answer 1

After writing your 4 “main” categories to the columns, make an array that has a total of each column:

$columnTotals = array(10,6,12,13)
//example - obviously you'd use count or something to get the totals

Then, order your non-special categories in an array by largest to smallest:

$subcatTotals = array(18,15,13,12,8,4);
//here, you'll have to get the totals, then use an array sort to order them
//probably want an associative array so you know which total matches which cat.

Then, in a loop, add the first(largest) sub-category to the smallest column, and get a new total for that column.

This SHOULD give you the most even columns you can get – at least it has in all the made-up examples I’ve tried it with.