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[7/5] 128. Longest Consecutive Sequence

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128. Longest Consecutive Sequence

Medium

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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

Constraints:

0 <= nums.length <= 105
-109 <= nums[i] <= 109

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링크

https://leetcode.com/problemset/all/ 13668 회 연결

익명
작성일 2022.07.06 10:08

# O(n) Solution
class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        nums = set(nums)
        
        max_len = 0
        
        while nums:
            inc = dec = nums.pop()
            
            while inc + 1 in nums:
                inc += 1
                nums.remove(inc)
            while dec - 1 in nums:
                dec -= 1
                nums.remove(dec)
            
            max_len = max(max_len, inc - dec + 1)
        
        return max_len

# O(nlogn) solution
class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        
        nums = sorted(list(set(nums)))
        
        consequtive_num = 1
        max_consequtive_num = 1        
        for i in range(1, len(nums)):
            if (nums[i] == nums[i-1] + 1):
                consequtive_num += 1
            else:
                consequtive_num = 1
            max_consequtive_num = max(max_consequtive_num, consequtive_num)
                
        return 0 if len(nums)==0 else max_consequtive_num

[code=Python 3]# O(n) Solution
class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        nums = set(nums)
        
        max_len = 0
        
        while nums:
            inc = dec = nums.pop()
            
            while inc + 1 in nums:
                inc += 1
                nums.remove(inc)
            while dec - 1 in nums:
                dec -= 1
                nums.remove(dec)
            
            max_len = max(max_len, inc - dec + 1)
        
        return max_len

# O(nlogn) solution
class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        
        nums = sorted(list(set(nums)))
        
        consequtive_num = 1
        max_consequtive_num = 1        
        for i in range(1, len(nums)):
            if (nums[i] == nums[i-1] + 1):
                consequtive_num += 1
            else:
                consequtive_num = 1
            max_consequtive_num = max(max_consequtive_num, consequtive_num)
                
        return 0 if len(nums)==0 else max_consequtive_num[/code]