动态规划（最长递增子序列）---最长摆动子序列

最长摆动子序列

376. Wiggle Subsequence (Medium)

题目描述：

给定一个数组，求出其最长摆动子序列

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

代码：

public int wiggleMaxLength(int []nums){
    if(nums==null||nums.length==0)
        return 0;
    int up=1;
    int down=1;
    for(int i=1;i<nums.length;i++){
        if(nums[i]>nums[i-1]){
            up=down+1;
        }else if(nums[i]<nums[i-1]){
            down=up+1;
        }
    } 
    return Math.max(up,down);
}