Find absolute sum of minimum slice - codility

Question

Hi I've taken Codility test twice and scored 0. Please help me in solving the issue using JavaScript.

A non-empty array A consisting of N integers is given. A pair of integers (P, Q), such that 0 ≤ P ≤ Q < N, is called a slice of array A. The sum of a slice (P, Q) is the total of A[P] + A[P+1] + ... + A[Q].

A min abs slice is whose absolute sum is minimal.

For example, array A such that:

A[0] = 2
A[1] = -4
A[2] = 6
A[3] = -3
A[4] = 9

contains the following slice among others:

(0,1), whose absolute sum is = |2 + (-4)| = 2
(0,2), whose absolute sum is = |2 + (-4) + 6| = 4
(0,3), whose absolute sum is = |2 + (-4) + 6 + (-3)| = 1
(1,3), whose absolute sum is = |(-4) + 6 + (-3)| = 1
(1,4), whose absolute sum is = |(-4) + 6 + (-3) + 9| = 8
(4,4), whose absolute sum is = |9| = 9

Both slices (0,3) and (1,3) are min abs slice and their absolute sum equals 1.

Write a function:

function solution(A);

that, given a non-empty array A consisting of N integers, return the absolute sum of min abs slice.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [1..1,000,000];
each element of array A is an integer within the range [−10,000..10,000];

Here is my solution:

function solution(A, i = 0, sum = 0) {
  const N = A.length;
  if (N === 0) {
    return 0;
  }
  if (N == 1) {
    return Math.abs(A[0]);
  }
  A.sort();

  // All positives 
  if (A[0] >= 0 && A[N - 1] >= 0) {
    return Math.abs(A[0]);
  }
  // All Negatives
  if (A[0] <= 0 && A[N - 1] <= 0) {
    return Math.abs(A[N - 1]);
  }
  let currAbsSum = 0;
  let minAbsSum = Number.MAX_SAFE_INTEGER;
  for (var i = 0; i < N; i++) {
    let j = N - 1;
    while (j >= i) {
      currAbsSum = Math.abs(A[i] + A[j]);
      if (currAbsSum === 0) {
        return 0;
      }
      minAbsSum = Math.min(currAbsSum, minAbsSum);
      if (Math.abs(A[i]) > Math.abs(A[j])) {
        i++;
      } else {
        j--;
      }
    }
    if (A[i] > 0) break;
  }
  return minAbsSum;
}

Firstly, JavaScript and java are entirely different. Choose one. Second, you’ve provided no effort, just a problem, so therefore this will likely get downvoted and closed. — achAmháin, Aug 28 '18 at 18:47
Jeesh, the wording of that question is all over the place. Share a link to the original question. — Geuis, Aug 28 '18 at 18:49
@achAmháin Thanks for you swift response. I know the difference between Java & JavaScript and also I've already tried alot but unable solve it that why I've posted here. [Here](https://app.codility.com/c/feedback/4UX2QC-46U) is my score. — Anand Dev Singh, Aug 28 '18 at 18:53
@Geuis, It is a paid test and I can't open the link again as I've taken the test. Though If you want the code I wrote then I can add that in the post. — Anand Dev Singh, Aug 28 '18 at 18:56
First thing you do is sort the array, that already makes all the following logic invalid, changing the order of the input changes the slices you can make — juvian, Aug 28 '18 at 19:31
@juvian, Thanks for your input. I tried removing sort, even then it is not working, don't know why. Sorry, but, I'm not Good in algorithms. — Anand Dev Singh, Aug 28 '18 at 20:00
@Juvian, Thanks for the help, It seems like that but not the same because there he is looking for subarray whereas I'm looking for minimal abs sum itself. Also, I've tried the Javascript solution given by "sapy" over there but it is not working for me that definitely says my problem statement is different. — Anand Dev Singh, Aug 29 '18 at 05:11
@AnandDevSingh a subarray is the same as a slice in your problem, they are identical. I wouldn't trust the code there with 0 upvotes, the accepted answer explains the solution — juvian, Aug 29 '18 at 05:14
@juvian, Thanks for your swift response. I'm really trying hard to translate the "C++" solution into JavaScript but I fail. I really appreciate if you could help me. — Anand Dev Singh, Aug 29 '18 at 05:19
OK i have been looking into this but don't really think that this can be done in O(n) time complexity as stated in your question. Yet nowhere in the question (the one one you send me in a comment under my deleted answer) it states O(n). — Redu, Sep 01 '18 at 16:50

score 2 · Accepted Answer · edited Nov 13 '19 at 04:31

2

Here is a javascript version of O(n log n) answer taken from here:

function solution(A) {
 if (1 == A.length) return Math.abs(A[0]);

 let sums = new Array(A.length + 1);
 let minAbsSum = Number.MAX_SAFE_INTEGER;

 sums[0] = 0;
 
 for (var i = 0; i < A.length; i++) {
  sums[i + 1] = A[i] + sums[i];
 }

 sums.sort();

 for (var i = 1; i < sums.length; i++) {
  minAbsSum = Math.min(minAbsSum, Math.abs(sums[i] - sums[i - 1]));
 }
  
  return minAbsSum;
}

console.log(solution([2, -4, 6, -3, 9]))
console.log(solution([10, 10, 10, 10, 10, -50]))

edited Nov 13 '19 at 04:31

HCSF

2,387
1
14
40

answered Aug 29 '18 at 15:07

juvian

15,875
2
37
38

Thank you so much for your efforts. I would like to update you that I've taken the test again with your solution and its correctness is 80% and performance is 83% and it was enough to score the passing marks. Thanks again you rock. – Anand Dev Singh Sep 02 '18 at 16:00
That's it right there. Quick question: if my JS docs are correct, then for sum.sort(), "If omitted, the elements are sorted in ascending, ASCII character order", so sorting [0,3,6,9,13,18] that way gives me [0.13,18,3,6,9], which makes sense given the ASCII premise. Shouldn't a compare function be supplied in the sorting step? – Nick May 09 '19 at 19:17
@Nick thats for strings, these are numbers so it sorting it as it should. I don't remember if this is not in the specification, might just be a browser implementation to sort as numbers if the array has numbers – juvian May 09 '19 at 20:12

Find absolute sum of minimum slice - codility

1 Answers1