376. Wiggle Subsequence
作者:互联网
A sequence of numbers is called a wiggle sequence if the differences between successive numbers strictly alternate between positive and negative. The first difference (if one exists) may be either positive or negative. A sequence with fewer than two elements is trivially a wiggle sequence.
For example, [1,7,4,9,2,5]
is a wiggle sequence because the differences (6,-3,5,-7,3)
are alternately positive and negative. In contrast, [1,4,7,2,5]
and [1,7,4,5,5]
are not wiggle sequences, the first because its first two differences are positive and the second because its last difference is zero.
Given a sequence of integers, return the length of the longest subsequence that is a wiggle sequence. A subsequence is obtained by deleting some number of elements (eventually, also zero) from the original sequence, leaving the remaining elements in their original order.
Example 1:
Input: [1,7,4,9,2,5] Output: 6 Explanation: The entire sequence is a wiggle sequence.
Example 2:
Input: [1,17,5,10,13,15,10,5,16,8] Output: 7 Explanation: There are several subsequences that achieve this length. One is [1,17,10,13,10,16,8].
Example 3:
Input: [1,2,3,4,5,6,7,8,9] Output: 2
Follow up:
Can you do it in O(n) time?
class Solution(object): def wiggleMaxLength(self, nums): """ :type nums: List[int] :rtype: int """ n = len(nums) if n == 0: return 0 up = 1 down = 1 for i in range(1,n): if nums[i] > nums[i-1]: up = down + 1 elif nums[i] < nums[i-1]: down = up + 1 return max(up, down)
标签:wiggle,sequence,positive,nums,up,down,Wiggle,Subsequence,376 来源: https://www.cnblogs.com/boluo007/p/12547334.html