Problem Statement
Remove Duplicates from a Sorted Array
arr = [1,2,2,3,3,4,4,4,5]
Description - As you can see in the above array the...
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This will not work on objects sadly. It will work only if they refer to the same object
The point here is to write the algorithm yourself. In this case you are just delegating the problem to the library to solve.
Sets are built into JS, not a library.
The post states that this is specifically a JS interview question, not an algorithm or computer science test.
The question does not explicitly forbid anything, we've just been asked to solve the problem using JavaScript. Using this method would demonstrate to the interviewer that you have a grasp of modern JS, can use common sense by not reinventing the wheel, and have the sense to rely on an inbuilt language feature that is almost certainly faster than anything you could write (and presumably less likely to contain errors).
This is an interview situation where you should try to highlight everything you know, including being able to identify more efficient solutions.
If the interviewer actually wanted to test your ability to construct the algorithm yourself, they will ask for that explicitly - either in the question statement, or after you present them with the Sets based solution.
built into JS = standard LIBRARY. You get what I mean.
Yes, this post lacks a lot of details about the problem. It is actually a general problem, he is just using JS to solve it.
Before the author edited the post, he mentioned that the space complexity should be O(1) (this is what is required in many places where this problem is described) which your solution does not meet.
You can see more details about the problem here:
interviewbit.com/problems/remove-d...
leetcode.com/problems/remove-dupli...
So, what's the overall performance of your solution? What's the time and space complexity?
The original problem requires you to use constant space and linear time, so that means you should work with the array in place and not allocate an extra array.
Sorry can you explain a little more in detail what is happening there? Thank you.
I can give it a go if that's ok :-)
let removeDuplicates = nums => ...is the same as
var removeDuplicates = function(nums) {...}but using arrow function expression syntax.
The function body
[...new Set(nums)]does 4 things:
a) creates a new Set using the original nums array as source
b) makes use of the property of Sets not allowing duplicate values to perform "automatic" deduplication
c) uses destructuring assignment syntax to turn the new Set back into an array
d) returns this new array
References:
developer.mozilla.org/en-US/docs/W...
developer.mozilla.org/en-US/docs/W...
developer.mozilla.org/en-US/docs/W...
PS: if you want to practice some warm up exercises of this sort... dev.to/jpantunes/js-warmup-exercis...
"Because each value in the Set has to be unique, the value equality will be checked." - from MDN. He is taking in the old array and spreading it into a new array while creating a new "Set" object which is forcing every value to be unique.
Based on the code you've given:
nums.sort(): Is O(nlogn) where n = size of original array. Because array is already sorted then you don't need to sort again anyway.You can also use a Map to keep track of already seen items.
The example shows integers but the problem statement does not mention any restrictions on the types. Will this work on any type?
If you want to know how to do it in constant space (and linear time):
You can think of
nextNonDuplicateas the index of a new array, if we were using a secondary array to store the non duplicated elements.From the description it sounds like this was supposed to be an in place removal of duplicates. If that's the case and given the time complexity, it's a much trickier algorithm.
Your solution is not using O(1) space. It's allocating a new array with at most N elements (worst case), so it's not constant.