Longest Consecutive Sequence

[cheatsheet1999]

Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
You must write an algorithm that runs in O(n) time.

---

Example 1:
Input: nums = [100,4,200,1,3,2]
Output: 4
Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.

Example 2:
Input: nums = [0,3,7,2,5,8,4,6,0,1]
Output: 9

---

/**
 * @param {number[]} nums
 * @return {number}
 */
var longestConsecutive = function(nums) {
    //First, we need a set that stores UNIQUE numbers
    let set = new Set(nums);
    //initialize the longest result to 0
    let longest = 0;
    for(let i of set) {
        //if this is not the start of consecutive sequence, skip this iteration
        if(set.has(nums[i] - 1)) continue;
        let length = 1;
        let curr = nums[i];
        //if we have a sequence, increase the length
        while(set.has(curr + 1)) {
            curr++;
            length++;
        }
        //if this is longest consecutive sequence
        longest = Math.max(length, longest);
    }
    return longest;
};