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3208. Alternating Groups II

MediumOpen on LeetCodeProblem statement

Problem Statement

3208. Alternating Groups II

Medium

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]:

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.

 

Example 1:

Input: colors = [0,1,0,1,0], k = 3

Output: 3

Explanation:

Alternating groups:

Example 2:

Input: colors = [0,1,0,0,1,0,1], k = 6

Output: 2

Explanation:

Alternating groups:

Example 3:

Input: colors = [1,1,0,1], k = 4

Output: 0

Explanation:

 

Constraints:

Java

Source file
class Solution {
    public int numberOfAlternatingGroups(int[] colors, int k) {
        int n = colors.length, streak = 0, numGrps = 0, lt = 0, rt = 0, prev = -1;
        for (; rt < n + k - 1; rt++) {
            if (colors[rt % n] == prev) {
                streak = 1;
                lt = rt;
            } else {
                streak++;
                prev = colors[rt % n];
                if (streak == k) {
                    // System.out.println(lt + "\t" + rt);
                    numGrps++;
                    lt++;
                    streak--;
                }
            }
        }
        return numGrps;
    }
}