文章作者：Tyan
博客：noahsnail.com  |  CSDN  |  简书

1. Description

Wiggle Subsequence

2. Solution

• First Version

class Solution {
public:
    int wiggleMaxLength(vector<int>& nums) {
        int length = nums.size();
        if(length < 2) {
            return length;
        }
        int positive[nums.size()] = {-1};
        int negative[nums.size()] = {1};
        int a = 0;
        int b = 0;
        for(int i = 1; i < length; i++) {
            int diff = nums[i] - nums[i - 1];
            int flag = 0;
            if(diff > 0) {
                flag = 1;
            }
            else if(diff < 0) {
                flag = -1;
            }
            if(flag == -positive[i - 1]) {
                positive[i] = flag;
                a++;
            }
            else {
                positive[i] = positive[i - 1];
            }
            if(flag == -negative[i - 1]) {
                negative[i] = flag;
                b++;
            }
            else {
                negative[i] = negative[i - 1];
            }
        }
        return a>b?(a+1):(b+1);
    }
};

• Second Version

class Solution {
public:
    int wiggleMaxLength(vector<int>& nums) {
        int length = nums.size();
        if(length < 2) {
            return length;
        }
        int positive = -1;
        int negative = 1;
        int a = 1;
        int b = 1;
        for(int i = 1; i < length; i++) {
            int diff = nums[i] - nums[i - 1];
            int flag = 0;
            if(diff > 0) {
                flag = 1;
            }
            else if(diff < 0) {
                flag = -1;
            }
            if(flag == -positive) {
                positive = flag;
                a++;
            }
            if(flag == -negative) {
                negative = flag;
                b++;
            }
        }
        return a>b?a:b;
    }
};

Reference

1. https://leetcode.com/problems/wiggle-subsequence/description/