Algorithms - Find the Symmetric Difference

JavaScript
1

Tell us what’s happening:

Can anyone tell why my code isn’t passing the tests?

As clunky as it is my code seems to be returning the correct output for the inputs given. I am copying and pasting each input directly and logging the output.

I have since come up with a better solution using reduce but it would still help to know what’s wrong here.

Your code so far

function sym(...args) {
  let sorted = []
  let longest = {length:0,i:0}
  let result = []

  for(let i=0;i < args.length;i++){
    let temp = args[i]
    if(args[i].length > longest.length){
      longest.length = args[i].length
      longest.i = i
    }

    let t = args[i]
    let o = Object.fromEntries(t.map(key => [key,key]))
    let a = Object.keys(o).map(key => o[key])

    sorted.push(a.sort(function(a,b){return a - b}))
  }

  let a = sorted.shift()
  let b = sorted.shift()
  
  result = [findDiff(a,b),...sorted]

  if(result.length < 2) {
    console.log("ARGUMENTS: ",...args)
    console.log("RESULTS",result[0])
    
    return result[0]
  }else
    sym(...result)
}

function findDiff(a,b){
  let result = []  
  
  while(a.length > 0 && b.length > 0){
    if(a[0] === b[0]){
      a.shift()
      b.shift()
    }else if(a[0] < b[0]){
      if(result.indexOf(a[0]) < 0)
        result.push(a[0])
      a.shift()
    }else{
      if(result.indexOf(a[0]) < 0)
        result.push(b[0])
      b.shift()
    }
  }

  result = [...result,...a,...b]
  return result
}
sym([1, 2, 5], [2, 3, 5], [3, 4, 5])

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Challenge Information:

Algorithms - Find the Symmetric Difference

2

It looks the problem is when there’s more than two sets to find difference. What part of code is responsible for returning result in such case?

3

It checks the first two sets, then replaces them with the result, if there is more than one set left, I use recursion to do it again until there is only the result left.

4

And what happens with the results of the recursive calls?

1 Like
5

The results from the recursive call is concatenated with the remainder sets that haven’t been calculated yet:

after that, it is checked to see if the array contains more than 1 set as I quoted above.

As far as I can tell, for any given input, the output is correct.

For the first test that breaks, the input is:
sym([1, 2, 5], [2, 3, 5], [3, 4, 5])

My logs say:
ARGUMENTS: [ 1, 2, 5 ] [ 2, 3, 5 ] [ 3, 4, 5 ]
ARGUMENTS: [ 1, 3 ] [ 3, 4, 5 ]
RESULTS [ 1, 4, 5 ]

But the test fails.

6

But there’s no return value from this call?

1 Like
7

AH THANK YOU!

I was a bit dense.

return sym(…result)

FIXED IT!