adding values that meet a certain condition javascript

Question

I have an array of strings array_strings and I want to get the maximum length of x consecutive values from the list and return a string. I have tried with this code but, its not working.

var myArr = ['we', 'make', 'the', 'best', 'dishes', 'in', 'cooking', 'class'];
x = 2;

function myFunc(array_strings, x) {
  // your code

  let val = '',
    y = 0;
  array_strings.sort((a, b) => {
    return a.length < b.length
  });
  if (array_strings.length > 0) {
    while (x) {
      val += array_strings[y];
      y++;
      x--;
    }
  }

  return val;
}
console.log(myFunc(myArr, x))
// expected output 'cookingclass'

on sorting, I cannot satisfy the consecutive order. Where am I going wrong?

If this is your entire code, then you're not actually calling the function. — , Sep 20 '18 at 19:05
Can you given some examples of the expected output? I'm not sure I understand the task. — Bergi, Sep 20 '18 at 19:09
Your [comparison function is insufficient](https://stackoverflow.com/q/24080785/1048572), but yeah you probably should not need to sort it at all. — Bergi, Sep 20 '18 at 19:10
You never declare the variable `arr`, used in `if (arr.length > 0)` — Barmar, Sep 20 '18 at 19:30
Why are you sorting the array in the first place? Then you no longer know which elements were originally consecutive. — Barmar, Sep 20 '18 at 19:30
@Barmar I've made an edit where the code is corrected the output is "cookingdishes" — JSmith, Sep 20 '18 at 19:31
@JSmith What does that have to do with either of my comments? Bergi asked for sample output, I already saw it. — Barmar, Sep 20 '18 at 19:34
@Barmar just to say that I've corrected the `arr` problem you've mentionned that's all. — JSmith, Sep 20 '18 at 19:36
I don't see the correction, it still says `while (arr.length > 0)`. — Barmar, Sep 20 '18 at 19:37

score 0 · Answer 1 · answered Sep 20 '18 at 19:24

To keep it simple, first get all possible values for x consecutive items.

function longestConsecutives(arr, x) {
    var consecutives = [];
    for (var i=0; i<arr.length-x; i++)
        consecutives.push(arr.slice(i, x).join(''));

and then search the one with maximum length amongst them:

    var longest = consecutives[0];
    for (var i=1; i<consecutives.length; i++)
        if (consecutives[i].length > longest.length)
            longest = consecutives[i];
    return longest;
}

There is also a more efficient approach to find the result, have a look at this for inspiration.

score 0 · Answer 2 · answered Sep 20 '18 at 19:34

I don't think there's any reason to sort for this. You can just move a sliding window of x length over the array and keep track of the longest sequence you've seen:

let array_strings = ['we', 'make', 'the', 'best', 'dishes', 'in', 'cooking', 'class']


function findMax(array_strings, x){
    let max_index = 0, max_length = 0

    for (let i= 0; i < array_strings.length - x + 1; i++){
        let length = array_strings.slice(i, i+x).reduce((l, c) => l + c.length, 0)
        if (length > max_length) {
            max_index = i,
            max_length = length
        }
    }
    return array_strings.slice(max_index, max_index + x)
}
console.log(findMax(array_strings,2))
console.log(findMax(array_strings,3))
console.log(findMax(array_strings,4))

score 0 · Answer 3 · answered Sep 20 '18 at 19:42

Rolling sum O(n) solution:

function findLongestConsec(arr, l) {
    var curSum = array_strings.slice(0, l).map(ele => ele.length).reduce((a, b) => a+b);
    var curMax = curSum;
    var curMaxIndex = 0;
    for (var i = 1; i < arr.length - l + 1; i++) {
        curSum = curMax - arr[i-1].length + arr[i+l-1].length;
        if (curSum > curMax) {
            curMax = curSum;
            curMaxIndex = i;
        }
    }
    return arr.slice(curMaxIndex, curMaxIndex + l).join('');
}

The previous solutions all involve string concatenation. I don't think it's worth doing it every time. We just have to keep track of the starting index of the longest subarray.

score 0 · Answer 4 · answered Sep 20 '18 at 19:45

Try this:

arr = ['we', 'make', 'the', 'best', 'dishes', 'in', 'cooking', 'class']
x = 2
var sorting = function (array_strings, items) {
    // your code

    let val = '', y = 0;
    const sort = array_strings.sort((a, b) => a.length < b.length);
    console.log({sort});
    
    if (arr.length > 0){
      while (items){
      val += array_strings[y];
      y++;
      items--;
     }
    }

 return val;
}

var s = sorting(arr,x);
console.log({s});

adding values that meet a certain condition javascript

4 Answers4