CODEWITHSUNDEEP
javascript
João Pedro
João Pedro

Reputation: 978

Remove the last element of an array while the sum of the array is bigger than a specific number

I'm trying to remove the last items of an array as long as the sum of the array is higher than a limit. The code I have works but seems to cause slow downs or crash. I was wondering if there's a more elegant solution.

let array = [166, 157, 251, 171, 191];
let limit = 400;

for (
  let sum = array.reduce((a, b) => a + b); sum > limit; sum = array.reduce((a, b) => a + b)
) {
  array.pop();
}

console.log(array);

Upvotes: 2

Views: 376

Answers (4)

Lev Izraelit
Lev Izraelit

Reputation: 532

To improve efficiency, as Barmar stated, you can calculate the sum once and update it in each loop iteration. I believe a while loop expresses this idea the most clearly:

const arr = [166, 157, 251, 171, 191];
const limit = 400;

let sum = arr.reduce((a, b) => a + b)
while (sum > limit) {
  const lastNum = arr.pop();
  sum -= lastNum;
}

console.log(arr)

Upvotes: 2

Pavan J
Pavan J

Reputation: 353

This should work:

const threshold = 10;
let sum = 0;
arr = [1, 2, 3, 5, 6, 3];
const filteredArray = arr.filter((el) => {
  sum += el;
  return sum <= threshold;
});

Upvotes: 0

DecPK
DecPK

Reputation: 25406

This solution will achieve the result in O(n)

You can achieve the result If you loop over the array and remember the last total i.e currentTotal and stop the iteration and break out from the loop if

currentTotal + val > limit

else add the current value in currentTotal and push that element in the result array.

let array = [166, 157, 251, 171, 191];
let limit = 400;

let currentTotal = 0;
const result = [];

for (let val of array) {
  if (currentTotal + val > limit) {
    break;
  }
  result.push(val);
  currentTotal += val;
}

console.log(result);

Upvotes: 3

Barmar
Barmar

Reputation: 782130

You don't need to sum the entire array each time through the loop. Calculate the sum once at the beginning. Then subtract the element that you removed from the sum.

let array = [166, 157, 251, 171, 191];
let limit = 400;

for (let sum = array.reduce((a, b) => a + b); sum > limit; sum -= array.pop()) {}

console.log(array);

Upvotes: 4

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