class Solution {
    
    
public:
    int wiggleMaxLength(vector<int>& nums) {
    
    
        int preDiff = 0, curDiff = 0;
        int count = 0;
        for (int i = 0; i < nums.size(); i++) {
    
    
            if (i == 0) {
    
    
                count++;
                continue;
            }
            curDiff = nums[i] - nums[i-1];
            if ((curDiff > 0 && preDiff <= 0) || (curDiff < 0 && preDiff >= 0)) {
    
    
                count++;
                preDiff = curDiff;
            }
        }
        return count;
    }
};