LeetCode 26: Remove Duplicates from Sorted Array

#javascript #algorithms #programming #node

Let's talk about removing duplicates. Normally, removing duplicates from a sorted array would be quick work. You just add each value to a set. Since all values in sets must be unique you simply return the values contained in the set. This was not a valid solution for this problem.

The problem states that you have to modify the array in place. That means I can't create another data structure to store my values when I find any duplicates. Admittedly, the solution is still straightforward. I have not had the pleasure of using the splice() function in JavaScript too many times, so it took me a bit longer than I would have liked until I rediscovered it.

Now we will build the solution. I'll explain it first with some pseudocode, and then present the actual code below.

Loop through the array
The array size will change when we remove an element, so we need to use a variable to store the initial array length
check if i is greater than or equal to array.length
break if true
check if i equals i+1
if true, remove element at index i with splice()
decrement i to recheck that same position in case of further duplicates

Like I said, pretty straightforward. I tend to overthink these algorithm problems. That's why I'm practicing!

Solution:

var removeDuplicates = function(nums) {
    let numsLength = nums.length;
    for (let i = 0; i < numsLength; i++) {
        if (i >= nums.length) {
            break;
        }
        if (nums[i] === nums[i + 1]) {
            nums.splice(i, 1);
            i--;
        }
    }
};