LeetCode 3206: Alternating Groups I Solution

Master LeetCode problem 3206 (Alternating Groups I), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

3206. Alternating Groups I

Easy

Array Sliding Window

Problem Explanation

Explanation

To solve this problem, we can iterate through the array of colors and check every group of 3 contiguous tiles. If the colors in the group form an alternating group, we increment the count of alternating groups. We can check if a group is alternating by comparing the colors of the left and right tiles with the middle tile. To handle the circular nature of the circle, we can consider wrapping around the array indices.

Algorithm:

Initialize a variable count to 0 to store the number of alternating groups.
Iterate through the colors array.
For each index i, check if colors at indices i, (i+1)%n, and (i+2)%n form an alternating group.
If the colors form an alternating group, increment count.
Return the final count as the result.

Time Complexity

The time complexity of this algorithm is O(n), where n is the number of colors in the input array.

Space Complexity

The space complexity is O(1) as we are using a constant amount of extra space.

Solution Code

class Solution {
    public int countAlternatingGroups(int[] colors) {
        int count = 0;
        int n = colors.length;
        for (int i = 0; i < n; i++) {
            if (colors[i] != colors[(i + 1) % n] && colors[(i + 1) % n] != colors[(i + 2) % n]) {
                count++;
            }
        }
        return count;
    }
}

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