Table of Contents

## Question

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:4Explanation: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

**Constraints:**

`0 <= nums.length <= 10`

^{5}`-10`

^{9}<= nums[i] <= 10^{9}

## Python Solution

from heapq import heappush,heappop,heapify class Solution: def longestConsecutive(self, nums: List[int]) -> int: nums = list(set(nums)) heapify(nums) prev = -float('inf') r = 1 m = 0 i = len(nums)-1 while i!=-1: curr = heappop(nums) if prev+1==curr: r+=1 else: r = 1 m = max(m,r) prev = curr i-=1 return m