Find Score of an Array After Marking All Elements

class Solution {
public:
    long long calculateSum(vector<int>& elements) {
        long long result = 0;
        for (int index = 0; index < elements.size(); index += 2) {
            int startIndex = index;
            while (index + 1 < elements.size() && elements[index + 1] < elements[index]) {
                index++;
            }
            for (int j = index; j >= startIndex; j -= 2) {
                result += elements[j];
            }
        }
        return result;
    }
};

This C++ solution focuses on calculating the sum of elements in a given array with a special marking condition. The function calculateSum is implemented in a class named Solution. Within the function, an accumulator variable result is initialized to zero, used to store the sum of marked elements.

To achieve the desired sum, the function employs a nested loop mechanism:

• The outer loop iterates through the array, skipping every second element (index += 2). This selective iteration marks the starting point (startIndex) of a potential scoring sequence.
• Once the start is marked, an inner while loop searches forward in the array from the current index as long as consecutive elements decrease in value (elements[index + 1] < elements[index]). The purpose of this loop is to extend the range of scoring elements up to the point before the sequence stops decreasing.
• A nested for loop then iterates backward within the identified range of elements, once again skipping every second element (j -= 2). This loop adds the values of the marked elements to the result.

The function ultimately returns the result, which constitutes the sum of all specially marked elements following the described pattern. This approach ensures that elements are selected based on the specific pattern of decreasing sequences separated by intervals of at least one unselected element.

This calculated sum is reported as the final score after marking all elements based on the defined rules. This method allows efficient identification and summation of parts of the array that fit the specified marking criteria.

class Solution {

    public long calculateTotal(int[] nums) {
        long total = 0;
        for (int idx = 0; idx < nums.length; idx += 2) {
            int start = idx;
            while (idx + 1 < nums.length && nums[idx + 1] < nums[idx]) {
                idx++;
            }
            for (
                int k = idx;
                k >= start;
                k -= 2
            ) {
                total += nums[k];
            }
        }
        return total;
    }
}

This Java program defines a method calculateTotal inside a class named Solution, which computes the score of an array after marking elements based on specific conditions. The process involves iterating through the array and summing up certain values strategically to determine the total score. The method accepts an integer array as its parameter.

Here’s a breakdown of how the code works:

• Declare a long variable total to accumulate the scores, initialized to 0.
• Use a for loop to traverse through the array. The loop increments by 2 for each iteration, focusing on elements at even indices.
• Inside the loop, identify segments of the array where elements decrease sequentially. This is done using a while loop that extends the idx as long as the next element is smaller than the current one.
• Once a decreasing sequence ends, another nested loop sums up every second element from the sequence, starting from the end of the segment back to the start.
• This calculation considers only elements at even positions within the identified segments, effectively marking them and adding to the total score.
• Finally, the method returns the accumulated total.

This logic ensures an efficient computation of scores based on the defined rules of marking, making it effective for scenarios that require selective aggregation based on array patterns.

class Solution:
    def computeSum(self, elements: List[int]) -> int:
        total_sum = 0
        index = 0
        while index < len(elements):
            segment_begin = index
            while index + 1 < len(elements) and elements[index + 1] < elements[index]:
                index += 1
            segment_end = index
            while segment_end >= segment_begin:
                total_sum += elements[segment_end]
                segment_end -= 2
            index += 2
        return total_sum

The given Python3 code provides a method to compute the sum of certain elements from an array, based on specific conditions. This entails iterating through the array to find segments where elements continuously descend and then summing every other element in such segments.

• The computeSum method from the Solution class takes an array, elements, as input.
• It initializes total_sum to zero, which will hold the running total of the sum satisfying the conditions set forth.
• The code uses a while loop to traverse through the array. For every element, it identifies segments where the value of the subsequent element is less than the current one.
• Once a segment is identified, another loop counts backwards from the segment's end, adding alternate elements (skipping one between additions) to total_sum.
• After processing a complete segment, the outer loop skips to the next possible segment starting point by incrementing the index by 2.
• Finally, the computeSum method returns the accumulated total_sum, which represents the sum of all eligible elements based on the defined segments and skip pattern.

This ensures efficient and tailored addition of array values as per specified conditions, providing a comprehensive method to evaluate segments and achieve the desired summation.