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[7/5] 128. Longest Consecutive Sequence

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작성일 2022.07.05 20:14

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128. Longest Consecutive Sequence

Medium

11658500Add to ListShare

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/ 12585 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]