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Daily Challenge #154 - Stable Arrangement

thepracticaldev profile image dev.to staff ・1 min read

Setup

Write a function that will take an array of unique positive integers, and two additional integers as input. With this method, try to rearrange the array so that the sum of any n consecutive values does not exceed q.

Test constraints:

  • 2 <= n <= 6
  • 4 <= arr length < 12
  • n < arr length
  • Every value in arr will be less than q

Example

const arr = [3,5,7,1,6,8,2,4];
const n = 3; // span length
const q = 13; // weight threshold
solver(arr,n,q); // one possible solution: [4,7,1,5,6,2,3,8] 

Tests

[[3,5,7,1,6,8,2,4], 3, 13]

[[7,12,6,10,3,8,5,4,13,2,9], 4, 28]

[[9,16,11,6,15,14,19,3,12,18,7], 3, 35]

Good luck!


This challenge comes from docgunthrop on CodeWars. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

Want to propose a challenge idea for a future post? Email yo+challenge@dev.to with your suggestions!

Discussion

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fitsum profile image
fitsum
const f = (ar, n, q) => {
  if (n >= ar.length)
    return `${n} is more than ${ar.length}`;

 const sorted = ar.sort((a, b) => a - b);
  do {
    sorted.pop()
  }
  while (sorted.reduce((acc, each) => acc + each) > q);
  return sorted;
}

//eg
const result = f([10, 4, 13, 11, 2], 4, 20);

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idanarye profile image
Idan Arye

You are pop()ing items from the array without push()ing them back. Shouldn't the result contain all the elements of the original array?

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fitsum profile image
fitsum

ah. good point

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centanomics profile image
Cent

JS, had to google how to use a reducer for this one since it was simpler than my original idea to add all of the values

CodePen


const solver = (arr, n, q) => {
  // console.log("Welcome to the stable arrangment, your quota is:", q)
  for(let i = 0; i < arr.length - n + 1; i++) {
    let j = 0;
    do {
      const set = arr.slice(i, i+n).reduce((acc, val) => acc + val);
      if(set > q) {
        let value = arr.shift();
        arr.push(value);
      } else {
        // console.log(arr.slice(i, i+n),set);
        break;
      }
    } while(true);
  }
  return arr;
}

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nickholmesde profile image
Nick Holmes

Your "shift then push" approach changes the positions of the values in the array, but not their order. Conceptually, (shift then push) * length gets you back were you started.

As the task asks you to "rearrange" the values, which I take to mean "change the order" of the values, and you are not changing the order, it would seem that this approach cannot work in the general case.

For example, in the case of

solver([3,5,7,1,6,8,2,4], 3, 13);

the return value is

[7,1,6,8,2,4,3,5]

This is clearly the input rotated 2 to the left, and the first slice [7, 1, 6] sums to 14 (when it should be <= 13).

(In the worst case, where no slice of the input sums <= q, your function will run forever).