如何将数组分成两半，直到达到一定大小的块？

Question

I have an array with a variable length that is greater than 3 and can be odd or even.

For example: var arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];

Now I want to split that array into halves.

['a', 'b', 'c', 'd', 'e'] and ['f', 'g', 'h', 'i', 'j']

Next I want to split those chunks into halves and to keep doing that until the chunks have a length of 3 or 2.

Finally I want to store those chunks in a new array.

var newarr = [['a','b','c'],['d','e'],['f','g','h'],['i','j']];

How would I do this?

Answer 1

A self-suggesting way to do this is to use a recursive function F: for an input array arr if its length is <= 3 then the result is [arr] , otherwise it is F(first_half_of_arr) concatenated with F(second_half_of_arr) .

In code this translates to:

function recursiveSplit(arr) { 
    return arr.length <= 3 ? [arr] : 
        recursiveSplit(arr.slice(0, Math.ceil(arr.length / 2)))
        .concat(recursiveSplit(arr.slice(Math.ceil(arr.length / 2))));
}

You can exclude the Math.ceil calls, but if you do you are going to get the 2-length chunks before the 3-length ones in your result.

Now in practice an iterative implementation should be much more performant than a recursive one because it won't need to create and abandon small arrays entirely, so if this is expected to operate on large arrays you should probably stay away from recursion.

Answer 2

var arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];
var arr1 = arr.splice(0, Math.ceil(arr.length / 2));

That will split an array in half, so now arr contain second half of original array and arr1 contains first half.

You should be able to just repeat in a while loop:

while (arr > 3) {
    //continue splicing
}

If you don't think this answer is good enough (It probably makes no sense to anyone other than me, I am so tired right now) please just comment rather than disliking.