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128. Longest Consecutive Sequence	https://leetcode.com/problems/longest-consecutive-sequence/description/	2024-02-20 20:53:00 +0800	2024-02-20 20:53:00 +0800	false	Kimi.Tsai	https://kimi0230.github.io/	0128.Longest-Consecutive-Sequence			LeetCode Go Medium Longest Consecutive Sequence Array Hash Table Union Find Amazon Microsoft Google Adobe Spotify	LeetCode			false	false	false	true	true	true	true	false	false	enable auto true true	copy maxShownLines true 200	enable		enable true	enable true	css js	images

128. Longest Consecutive Sequence

題目

給定一個未排序的整數數位列 nums ，找出數字連續的最長序列（不要求序列元素在原陣列中連續）的長度。 請你設計並實現時間複雜度為 O(n) 的演演算法解決此問題。

題目大意

解題思路

Big O

時間複雜 : O(n) 空間複雜 : O(n)

來源

• https://leetcode.com/problems/longest-consecutive-sequence/description/
• https://leetcode.cn/problems/longest-consecutive-sequence/description/

解答

https://github.com/kimi0230/LeetcodeGolang/blob/master/Leetcode/0128.Longest-Consecutive-Sequence/main.go

package longestconsecutivesequence

// 時間複雜 O(), 空間複雜 O()
func longestConsecutive(nums []int) int {
	m := make(map[int]struct{}, len(nums))
	for _, num := range nums {
		m[num] = struct{}{}
	}
	result := 0
	for v := range m {
		// 如果沒找到該數字的前一個數字, 則把該數字刀做連續序列的第一個數
		if _, ok := m[v-1]; !ok {
			length := 1
			for _, exit := m[v+length]; exit; _, exit = m[v+length] {
				length++
			}
			if result < length {
				result = length
			}
		}
	}
	return result
}

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