# ---
# title: 128. Longest Consecutive Sequence
# id: problem128
# author: Tian Jun
# date: 2020-10-31
# difficulty: Hard
# categories: Array, Union Find
# link: <https://leetcode.com/problems/longest-consecutive-sequence/description/>
# hidden: true
# ---
# 
# Given an unsorted array of integers `nums`, return _the length of the longest
# consecutive elements sequence._
# 
# **Follow up:**  Could you implement the `O(n)` solution?
# 
# 
# 
# **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
#     
# 
# 
# 
# **Constraints:**
# 
#   * `0 <= nums.length <= 104`
#   * `-109 <= nums[i] <= 109`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
