376. Wiggle Subsequence

最新推荐文章于 2021-02-02 16:30:19 发布

原创最新推荐文章于 2021-02-02 16:30:19 发布 · 246 阅读

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本文介绍了一种寻找最长摆动子序列的有效算法。摆动序列是指一个数列中相邻两个数之间的差值严格交替正负的序列。文章通过示例说明了何为摆动序列，并给出了一段C++代码实现，该算法能够处理任意整数序列，返回最长摆动子序列的长度。

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.

class Solution {
public:
    int wiggleMaxLength(vector<int>& nums) {
        int n = nums.size();
    	if(n == 0) return 0;
        int s1[n],s2[n];
        s1[0] = 1;
        s2[0] = 1;
        for(int i = 1; i < n; i ++)
        {
        	if(nums[i] > nums[i-1])
        	{
        		s1[i] = s2[i - 1] + 1;
        		s2[i] = s2[i - 1];
        	}
        	else if(nums[i] < nums[i-1])
        	{
        		s2[i] = s1[i - 1] + 1;
        		s1[i] = s1[i - 1];        		
        	}
        	else
        	{
        		s1[i] = s1[i-1];
        		s2[i] = s2[i-1];
        	}
        }
        return max(s1[n-1],s2[n-1]);
    }
};