Solving LeetCode 136 in JavaScript (Single Number)

In this video I solve LeetCode problem 136 (Single Number) with the JavaScript programming language. This question has previously appeared during Amazon coding interviews.

I start by helping you understand what the problem is asking for, then I will go over the pseudo-code/logic for a solution, and finally I will write the solution code explaining each line, step-by-step.

Using my simple and easy-to-understand methodology, I make difficult and complex interview questions *incredibly* easy to understand. So easy in fact, that even your grandma could do it! 👵🏻

I will be solving a new problem EVERY WEEK, so be sure to smash that subscribe button and hit the notification bell so you don't miss a single one! 😀

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#programming #codinginterview #leetcode

[somebody-]

You must implement a solution with a linear runtime complexity and use only constant extra space.

[suvajitchakrabarty]

If in case anyone is interested, the O(1) space complexity requires some bit manipulation. Essentially if you XOR a number with itself, it returns zero, and if you XOR a number with zero, it returns the number itself.
So if you had the following numbers in the list - 3, 3, 2, the XOR between 3 and 3 would return 0, and then XORing 0 with 2 would return 2. Hence if you did a XOR for all numbers in a list which contains 2 of each numbers except for the one number, then you'd get back the number which occurs once.

The code is pretty straightforward since you only need to do a XOR for every number, and return the result.
Code in Javascript -

var singleNumber = function(nums) {
let res = nums[0];

for (let i = 1; i<nums.length; i++) {
res = res ^ nums[i];
}

return res;
};

[BabeCrs]

it asks it to be in O(1) space complexity. How would you adapt this for that

[jinbo]

ht[num] = ht[num] +1 || 1 can you please explain more on this part?

[feng]

isn't const ht an Object? When should we use map or object?