LeetCode-in-Java

3206. Alternating Groups I

Easy

There is a circle of red and blue tiles. You are given an array of integers colors. The color of tile i is represented by colors[i]:

• colors[i] == 0 means that tile i is red.
• colors[i] == 1 means that tile i is blue.

Every 3 contiguous tiles in the circle with alternating colors (the middle tile has a different color from its left and right tiles) is called an alternating group.

Return the number of alternating groups.

Note that since colors represents a circle, the first and the last tiles are considered to be next to each other.

Example 1:

Input: colors = [1,1,1]

Output: 0

Explanation:

Example 2:

Input: colors = [0,1,0,0,1]

Output: 3

Explanation:

Alternating groups:

Constraints:

• 3 <= colors.length <= 100
• 0 <= colors[i] <= 1

Solution

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

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