Longest Consecutive Sequence

// Longest Consecutive Sequence
// https://leetcode.com/problems/longest-consecutive-sequence/description/
/*
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
*/

/* links : https://youtu.be/qgizvmgeyUM
Apporch is  we are inserting all values into the set
then we are finding (num-1) values in set are not , when it is not found in the set we are going to (num+1)
then we (num+1) we count the value and finally we will return the value */



class Main {
   public int longestConsecutive(int[] nums) {
    HashSet<Integer> set = new HashSet<>();
    for(int num: nums) set.add(num);
    int result = 0;
 
    for(int num: nums){
        if(!set.contains(num-1)){
            int currentstreak=num;
            int streak=1;

            while(set.contains(currentstreak+1)){
                currentstreak+=1;
                streak+=1;
            }
            result=Math.max(result,streak);
        }
    }
 
    return result;

}}