split array of objects into three seperate array based on a property

Question

I have a array of objects with property of id and size. Sum of objects size equals to 78 and I want to split this objects by three array. But I want to split possibly equal sum of size (~ 78/3 +-).

I have a this array of objects,

[
 {'id': '1', 'size': '10'},
 {'id': '2', 'size': '4'},
 {'id': '3', 'size': '6'},
 {'id': '4', 'size': '21'},
 {'id': '5', 'size': '2'},
 {'id': '6', 'size': '1'},
 {'id': '7', 'size': '6'},
 {'id': '8', 'size': '7'},
 {'id': '9', 'size': '8'},
 {'id': '1', 'size': '13'}
]

And I want

[
 [
  {'id': '4', 'size': '21'},
  {'id': '2', 'size': '4'}, 
  {'id': '6', 'size': '1'},
 ],
 [
  {'id': '1', 'size': '13'},
  {'id': '1', 'size': '10'},
  {'id': '5', 'size': '2'},
 ],
 [
  {'id': '3', 'size': '6'}, 
  {'id': '9', 'size': '8'},
  {'id': '7', 'size': '6'},
  {'id': '8', 'size': '7'},
 ]
]

I think [this post](https://stackoverflow.com/q/19197836/1270789) will be a pointer in the right direction. If you have a specific question after trying to implement one of the solutions in JavaScript, then we can help. — Ken Y-N, Jan 16 '19 at 06:46

score 0 · Answer 1 · answered Jan 16 '19 at 06:51

You can use a while() loop:

var arr = [
 {'id': '1', 'size': '10'},
 {'id': '2', 'size': '4'},
 {'id': '3', 'size': '6'},
 {'id': '4', 'size': '21'},
 {'id': '5', 'size': '2'},
 {'id': '6', 'size': '1'},
 {'id': '7', 'size': '6'},
 {'id': '8', 'size': '7'},
 {'id': '9', 'size': '8'},
 {'id': '1', 'size': '13'}
];
var i=0, res = [], tempArr=[];
while(i<arr.length){
  if(i!==0 && i%3 === 0){
    res.push(tempArr);
    tempArr = [arr[i]];
  } else {
    tempArr.push(arr[i]);
  }
  i++;
}
res.push(tempArr);
console.log(res);

Dmitry · Accepted Answer · 2019-01-16T08:32:09.600

This is an NP-complete problem so there is more then one solution. One approach I thought of is putting the bigger items first and then putting the smaller items where you have more space.

let items = [
    {'id': '1', 'size': 10},
    {'id': '2', 'size': 4},
    {'id': '3', 'size': 6},
    {'id': '4', 'size': 21},
    {'id': '5', 'size': 2},
    {'id': '6', 'size': 1},
    {'id': '7', 'size': 6},
    {'id': '8', 'size': 7},
    {'id': '9', 'size': 8},
    {'id': '1', 'size': 13}
];
//sort the array by size in reverse order
items.sort((a, b)=> b.size - a.size);
//array of sums
let sums = [0,0,0];
//final array of 3 arrays
let arrays = [[],[],[]];
for (let item of items) {
    //get index of the smallest sum
    let index =  sums.indexOf(Math.min.apply(null,sums));
    //add current item size to corresponding sum
    sums[index] += item.size;
    //add item to corresponding array
    arrays[index].push(item);
}
console.log(arrays);
console.log(sums);

split array of objects into three seperate array based on a property

2 Answers2