128.最长连续序列.py

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# @lc app=leetcode.cn id=128 lang=python3
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# [128] 最长连续序列
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# https://leetcode.cn/problems/longest-consecutive-sequence/description/
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# algorithms
# Medium (55.13%)
# Likes:    1431
# Dislikes: 0
# Total Accepted:    326.1K
# Total Submissions: 591.4K
# Testcase Example:  '[100,4,200,1,3,2]'
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# 给定一个未排序的整数数组 nums ，找出数字连续的最长序列（不要求序列元素在原数组中连续）的长度。
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# 请你设计并实现时间复杂度为 O(n) 的算法解决此问题。
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# 示例 1：
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# 输入：nums = [100,4,200,1,3,2]
# 输出：4
# 解释：最长数字连续序列是 [1, 2, 3, 4]。它的长度为 4。
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# 示例 2：
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# 输入：nums = [0,3,7,2,5,8,4,6,0,1]
# 输出：9
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# 提示：
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# 0 
# -10^9 
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# @lc code=start
class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        # 1. 哈希表 O(N) O(N)
        max_len = 0
        nums_set = set(nums)
        for num in nums_set:
            if num - 1 not in nums_set:
                cur_num = num
                cur_len = 1
                while cur_num + 1 in nums_set:
                    cur_num += 1
                    cur_len += 1
                max_len = max(max_len, cur_len)
        return max_len
# @lc code=end