Alternating Groups II

class Solution {
public:
    int countKGroups(vector<int>& paint, int threshold) {
        int total = paint.size();
        int count = 0;
        int sequenceLength = 1;
        int previousColor = paint[0];

        for (int j = 1; j < total + threshold - 1; j++) {
            int currentIndex = j % total;

            if (paint[currentIndex] == previousColor) {
                sequenceLength = 1;
                previousColor = paint[currentIndex];
                continue;
            }

            sequenceLength++;

            if (sequenceLength >= threshold) {
                count++;
            }

            previousColor = paint[currentIndex];
        }

        return count;
    }
};

The provided C++ code defines a class named Solution with a function countKGroups that takes two parameters: a vector of integers named paint representing colors, and an integer threshold representing the minimum sequence length required to form a valid group. The purpose of this function is to count how many groups of alternating colors in the vector meet or exceed the specified threshold.

Here's an outline of how the function operates:

• Initializes several variables:

  • total captures the total number of elements in paint.
  • count accumulates the number of valid groups.
  • sequenceLength captures the current length of alternating colors.
  • previousColor to track the color of the last inspected element.

• Loops through each color in the paint array, considering the threshold:

  • Uses modulo operation to handle scenarios that exceed array bounds.
  • Checks if the current color at currentIndex is the same as previousColor.
    • If true, it resets sequenceLength to 1.
    • If false, increments sequenceLength.
  • Evaluates if sequenceLength has met or exceeded the threshold to increase the count of valid groups.
  • Updates previousColor for the next iteration.

• Finally, the function returns the count of valid alternating groups that meet or exceed the threshold.

This approach ensures that the function efficiently checks each color sequence against the threshold, looping over paint while accounting for wrap-around using modulo, and keeps track of consecutive color changes to determine the count of valid groups.

class Solution {

    public int countAlternatingGroups(int[] array, int minimumLength) {
        int arrLength = array.length;
        int totalCount = 0;
        int currentSequenceLength = 1;
        int previousElement = array[0];

        for (int j = 1; j < arrLength + minimumLength - 1; j++) {
            int currentIndex = j % arrLength;

            if (array[currentIndex] == previousElement) {
                currentSequenceLength = 1;
                previousElement = array[currentIndex];
                continue;
            }

            currentSequenceLength += 1;

            if (currentSequenceLength >= minimumLength) {
                totalCount++;
            }

            previousElement = array[currentIndex];
        }

        return totalCount;
    }
}

This solution is designed to count the number of alternating groups in a circular array where a group must have a minimum length as specified. The array is assessed in terms of its pattern changes, pinpointing where values switch from one to another consecutively. The circular nature requires wrapping around the array to ensure all potential groups are counted, which may extend beyond the physical end of the array structure.

The essential steps of the implemented method countAlternatingGroups include:

1. Initialize variables for counting total groups (totalCount), tracking the current length of a sequence (currentSequenceLength), and storing the previously encountered array element (previousElement).
2. Iterate over the array using an extended range to accommodate the circular nature. This is achieved using the modulo operator on the current index, ensuring it wraps around if it surpasses the array's actual boundary.
3. Compare the current element to the previous one. If they are the same, reset the current sequence length to 1, updating previousElement. If different, increase the currentSequenceLength.
4. If this sequence length meets or exceeds the specified minimumLength, increment the totalCount.
5. Update previousElement with the current array element for subsequent comparisons.

The primary goal of this method rests on effectively dealing with patterns in a circular sequence, making it useful in applications where cyclical data patterns are analyzed, ensuring groups or sequences meet a certain length criterion. The solution's modular nature means it can adapt easily to variations in input size and group length requirements.

class Solution:
    def countAlternatingSubarrays(self, color_list: List[int], min_length: int) -> int:
        total_colors = len(color_list)
        count = 0
        sequence_length = 1
        previous_color = color_list[0]

        for index in range(1, total_colors + min_length - 1):
            circular_index = index % total_colors

            if color_list[circular_index] != previous_color:
                sequence_length += 1
                if sequence_length >= min_length:
                    count += 1
            else:
                sequence_length = 1

            previous_color = color_list[circular_index]

        return count

The Python program provided solves the problem of counting alternating subarrays within a circular list of colors. The function countAlternatingSubarrays accepts two parameters: color_list, a list of integers representing colors, and min_length, the minimum length of subarrays to consider.

• Start by initializing the total number of colors total_colors as the length of color_list.
• Set the initial count of valid subarrays count to zero and the initial sequence_length to one.
• Assign previous_color to the first color in the list to begin comparisons.

As you loop through the indices starting from one up to total_colors + min_length - 1, calculate circular_index using modulo to cycle back through the beginning of the list for circular behavior.

• If the color at circular_index differs from previous_color, increment the sequence_length. When the sequence_length is equal to or larger than min_length, increment the count.
• Reset sequence_length back to one if the current color is the same as previous_color.
• Update previous_color to the color at circular_index for the next cycle comparison.

Finally, output count which represents the number of valid alternating subarrays that meet the minimum length requirement.