[leetcode]Longest Consecutive Sequence @ Python
浏览数：48 /
时间：2015年06月08日
原题地址：https://oj.leetcode.com/problems/longest-consecutive-sequence/
题意：
Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
For example,
Given [100, 4, 200, 1, 3, 2],
The
longest consecutive elements sequence is [1, 2, 3, 4]. Return
its length: 4.
Your algorithm should run in O(n) complexity.
解题思路：使用一个哈希表，在Python中是字典dict数据类型。dict中的映射关系是{x in num：False}，这个表示num中的x元素没有被访问过，如果被访问过，则为True。如果x没有被访问过，检查x+1，x+2...，x-1，x-2是否在dict中，如果在dict中，就可以计数。最后可以求得最大长度。
代码：
class Solution: # @param num, a list of integer # @return an integer def longestConsecutive(self, num): dict = {x: False for x in num} # False means not visited maxLen = -1 for i in dict: if dict[i] == False: curr = i+1; lenright = 0 while curr in dict: lenright += 1; dict[curr] = True; curr += 1 curr = i-1; lenleft = 0 while curr in dict: lenleft += 1; dict[curr] = True; curr -= 1 maxLen = max(maxLen, lenleft+1+lenright) return maxLen
[leetcode]Longest Consecutive Sequence @ Python,古老的榕树,5-wow.com
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