Question

Find the element that appears once in an array where every other element appears twice - DSA and Algorithm - Javascript Problem and Solution

Answer 1

Sorting is one of the most expensive operations you can do and you’d have to operate on all of the elements before you could search your sorted array.

It would be better to hash the elements (using a set in Python) and do a membership search in a single run through.

The worst-case search time the hash and check method is ~O(N/2) and it will work on any data type that can be coerced to a string.

Answer 2

Gad that's a horrible solution! Don't sort.  Just push everything into a hash ( dictionary).

Start with empty dictionary or set


Loop over array:
  
    Check if element is in dictionary

         No: enter it into set as the key.

          Yes : delete key from set


Now the set keys are the elements that appear an odd number of times in list