Algorithms: Implement Merge Sort

JavaScript
1

Hi FCC,
So I have followed guide and solution, which made sense and it is still not working.
I have tried going over it and I don’t understand what is wrong.

2

If you share your code and explain what problems you are having, we can help you.

3

I was examining the solution code because I was stuck

Code is

//Merger function, which merges 2 sorted array into 1 sorted array
function merger(arr1, arr2){
  let i = 0, j = 0, mergedArr = [];
  while (i < arr1.length && j < arr2.length){
    if (arr1[i] > arr2[j]) mergedArr.push(arr2[j++]);
    else mergedArr.push(arr1[i++]);
  }
  while (i < arr1.length){
    mergedArr.push(arr1[i++]);
  }
  while (j < arr2.length){
    mergedArr.push(arr2[j++]);
  }
  return mergedArr;
}
function mergeSort(array) {
  //Array of length 1 is sorted so we return the same array back
  if (array.length == 1) return array;
  
  //Break down the array to half from middle into left and right
  let middle = Math.floor(array.length/2);
  let left = mergeSort(array.slice(0, middle));
  let right = mergeSort(array.slice(middle));  
  
  //Return the merged sorted array
  return merger(left, right);
}

When I test it it shows me an error

// running tests
mergeSort should not use the built-in .sort() method.
// tests completed
4

My guess is that there is imprecision in the test. If you remove the comments that have “sort” in them, does it still say that?

5

That did it!
Thanks Ariel!

6

If you’ve got a minute, it would be helpful to search through the GitHub Issues to see if it’s already been reported. If not you can report that the tests break with “sort” in the comments.

7

Just did

8

Awesome! Thanks.

Happy coding. :slight_smile: