JavaScript LeetCode Contains Duplicate

Introduction

Continuing through the problems of LeetCode. I am not haphazardly selecting any questions. I am following along with this list for those that were curious:

techinterviewhandbook.org/best-practice-que..

Prompt

Given an integer array nums , return true if any value appears at least twice in the array, and return false if every element is distinct.

Example 1:

Input: nums = [1,2,3,1]
Output: true

At first glance, the problem seems to be pretty simple. The idea here is to iterate over the array and find any duplicates. There's a bit of a cheat code we can use with JavaScript in this one.

First Solution (cheating)

There is a standard built-in object for JavaScript called [Set] (developer.mozilla.org/en-US/docs/Web/JavaSc..)

But what does this object do?

Set objects are collections of values. You can iterate through the elements of a set in insertion order. A value in the Set may only occur once; it is unique in the Set's collection.

Knowing this, the only thing we need to do is convert our array into a Set and compare its length with the original number array length.

var containsDuplicate = function(nums) {
    const set = new Set([...nums]);
    return set.size != nums.length;
};

Converting an array into a Set is simple, just spread it in a new array in the Set constructor. It has a property to calculate the size (number of items). We just have to compare that with the length of the original array, nums.

return set.size != nums.length;

Second Solution

Much like our (first solution)[relatablecode.com/javascript-leetcode-two-s.. we can create a hash table of our array as we're iterating and evaluate it in place.

var containsDuplicate = function(nums) {
   const hashTable = new Map();

    for(let i = 0; i < nums.length; i++) {
        if(hashTable.has(nums[i])) return true;
        else hashTable.set(nums[i], true);

    }
    return false;
};

To break this down a little bit: we first iterate over the array of numbers. If the map already has the value then we return true. We check this with the .has property of maps

if(hashtable.has(nums[i]) return true;

Otherwise, we add it to the map and move on.

else hashTable.set(nums[i], true);

The value is pretty irrelevant as we don't really care much for it. There probably is a data structure more suited here.

JavaScript LeetCode Contains Duplicate

The second article in my series of solving LeetCode problems with JavaScript. This time we're looking at removing duplicates from an array.

Introduction

Prompt

First Solution (cheating)

Second Solution

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