【LeetCode】 376. Wiggle Subsequence

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.

Examples:

Input: [1,7,4,9,2,5]
Output: 6
The entire sequence is a wiggle sequence.

Input: [1,17,5,10,13,15,10,5,16,8]
Output: 7
There are several subsequences that achieve this length. One is [1,17,10,13,10,16,8].

Input: [1,2,3,4,5,6,7,8,9]
Output: 2

Follow up:

Can you do it in O(n) time?

public class Solution {
public int wiggleMaxLength(int[] nums) {
int num1 = 1, num2 = 1;
for (int i = 1; i < nums.length; i++) {
if (nums[i] > nums[i - 1]) {
num1 = num2 + 1;
} else if (nums[i] < nums[i - 1]){
num2 = num1 + 1;
}
}
return Math.min(nums.length, Math.max(num1, num2));
}
}