s3208_alternating_groups_ii.go

/*
	https://leetcode.com/problems/alternating-groups-ii/description/

	There is a circle of red and blue tiles. You are given an array of integers
		colors and an integer k.
	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.

	An alternating group is every k contiguous tiles in the circle with alternating
		colors (each tile in the group
	except the first and last one has a different color from its left and right
		tiles).

	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.
*/

package solutions

func numberOfAlternatingGroups(colors []int, k int) int {
	res := 0
	n := len(colors)

	grLen := 1
	lastC := colors[0]

	for i := 0; i < n+k-1; i++ {
		idx := i % n
		if colors[idx] == lastC {
			grLen = 1
			lastC = colors[idx]
			continue
		}

		grLen++
		if grLen >= k {
			res++
		}
		lastC = colors[idx]
	}

	return res
}