# [3206\. Alternating Groups I](https://leetcode.com/problems/alternating-groups-i/)

:::spoiler Solution

class Solution {
public:
    int numberOfAlternatingGroups(vector<int>& colors)
    {
        int n = colors.size();
        for (int i = 0; i < n; ++i)
        {
            colors.push_back(colors[i]);
        }

        int cnt = 0;
        for (int i = 0; i < n; ++i)
        {
            if (colors[i] == colors[i + 2] && colors[i] != colors[i + 1])
            {
                ++cnt;
            }
        }
        return cnt;
        
    }
};

- 時間複雜度：$O(n)$
- 空間複雜度：$O(1)$
:::