128. 最长连续序列

原题

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

思路

集合

复杂度

时间：O(n)
空间：O(n)

Python代码

class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        # 将数组转为集合
        s = set(nums)
        ans = 0
        for n in s:            
            if n - 1 in s:
                # n不是连续数组的起点
                continue 
            next = n + 1 
            count = 1
            while next in s:
                count += 1 
                next += 1 
            ans = max(ans, count)
        return ans 

Go代码

func longestConsecutive(nums []int) int {
	// 将数组转为集合
	set := make(map[int]bool)
	for _, n := range nums {
		set[n] = true
	}
	ans := 0
    // 遍历集合
	for n := range set {
		if set[n-1] {
			// n不是连续数组的起点
			continue
		}
		next := n + 1
		count := 1
		for set[next] {
			count++
			next++
		}
		ans = max(ans, count)
	}
	return ans
}