LeetCode 3245: Alternating Groups III Solution

Master LeetCode problem 3245 (Alternating Groups III), a hard 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.

3245. Alternating Groups III

Hard

Array Binary Indexed Tree

Problem Explanation

Explanation

To solve this problem, we can follow these steps:

Create a function to count the number of alternating groups of a given size in the circular array.
Initialize a variable to store the count of alternating groups for each query of type 1.
For each query of type 1, call the function to count the alternating groups and store the count.
Return the counts of alternating groups for all queries of type 1.

Time Complexity: O(n) where n is the length of the colors array
Space Complexity: O(1)

Solution Code

class Solution {
    public List<Integer> countAlternatingGroups(int[] colors, int[][] queries) {
        List<Integer> result = new ArrayList<>();
        
        for (int[] query : queries) {
            if (query[0] == 1) {
                result.add(countAlternatingGroupsOfSize(colors, query[1]));
            } else if (query[0] == 2) {
                colors[query[1]] = query[2];
            }
        }
        
        return result;
    }
    
    private int countAlternatingGroupsOfSize(int[] colors, int size) {
        int count = 0;
        for (int i = 0; i < colors.length; i++) {
            int currColor = colors[i];
            int nextColor = colors[(i + 1) % colors.length];
            int groupSize = 2;
            while (nextColor != currColor && groupSize < size) {
                i++;
                currColor = nextColor;
                nextColor = colors[(i + 1) % colors.length];
                groupSize++;
            }
            if (groupSize == size) {
                count++;
            }
        }
        return count;
    }
}

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