Nested list to array

Question

I'm struggling with this kata that instructs me to create an array from a nested listed. I can find explanations for how to do this using Java but that's still a bit confusing for me.

This is what I've got so far...

function listToArray(list) {
  var listArray = [];
  for (var i = 0; i < list.length; i++) {
    listArray[i] = list.value(i);
  };
  return listArray;
};

The test cases...

var list1 = {value: 1, next: {value: 2, next: {value: 3, next: null}}};
var list2 = {value: "foo", next: {value: "bar", next: null}};

Test.assertSimilar(listToArray(list1), [1, 2, 3]);
Test.assertSimilar(listToArray(list2), ["foo", "bar"]);

Thanks for the help!

Dan D. · Accepted Answer · 2016-11-14 15:34:04Z

4

This is simply a linked list pointer chase:

function listToArray(list) {
  var listArray = [];
  while (list !== null) {
    listArray.push(list.value);
    list = list.next;
  }
  return listArray;
};

answered Nov 14, 2016 at 15:34

Dan D.

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1 Comment

wahoowa Over a year ago

Painfully simple. Thank you for your answer. Can you explain more about what a linked list pointer chase is or point me to where I can learn about it? A quick google search didn't show much.

kukkuz · Accepted Answer · 2016-11-14 15:36:30Z

1

Another solution using recursion:

var list1 = {value: 1, next: {value: 2, next: {value: 3, next: null}}};
var list2 = {value: "foo", next: {value: "bar", next: null}};

function convertToArray(list, result) {
  result.push(list.value);
  list.next && convertToArray(list.next,result);
  return result;
}

console.log(convertToArray(list1,[]));
console.log(convertToArray(list2,[]));

answered Nov 14, 2016 at 15:36

kukkuz

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Comments

Pranav C Balan · Accepted Answer · 2016-11-14 15:37:24Z

1

Do it with recursion

function listToArray(list) {
  var res = [];
  Object.keys(list).forEach(function(k) {
    if (typeof list[k] == 'object' && list[k] !== null)
      [].push.apply(res, listToArray(list[k]));
    else if (list[k] !== null)
      res.push(list[k]);
  });
  return res;
};

var list1 = {
  value: 1,
  next: {
    value: 2,
    next: {
      value: 3,
      next: null
    }
  }
};
var list2 = {
  value: "foo",
  next: {
    value: "bar",
    next: null
  }
};

console.log(listToArray(list1));
console.log(listToArray(list2));

edited Nov 14, 2016 at 15:37

answered Nov 14, 2016 at 15:31

Pranav C Balan

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Comments

Gavin · Accepted Answer · 2016-11-14 15:37:51Z

1

You just have to dig deeper into the object until you reach the null point.

var list1 = {value: 1, next: {value: 2, next: {value: 3, next: null}}};
var list2 = {value: "foo", next: {value: "bar", next: null}};

function listToArray(list) {
  var curr = list, arr = [];
  while (curr != null) {
    arr.push(curr.value);
    curr = curr.next;
  }
  return arr;
}

console.log(listToArray(list1));
console.log(listToArray(list2));

answered Nov 14, 2016 at 15:37

Gavin

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