Here is the solution for the "Maximum Weight Difference" problem on Codechef, explained step by step:

Step 1: Import the necessary libraries

include

include

using namespace std;

Step 2: Define the main function int main() {

Step 3: Declare the variables int t, n, k; cin >> t;

Step 4: Start the test cases loop while (t--) {

Step 5: Read the input values cin >> n >> k; int weights[n];

Step 6: Read the weights of the children for (int i = 0; i < n; i++) { cin >> weights[i]; }

Step 7: Sort the array in ascending order sort(weights, weights + n);

Step 8: Calculate the initial sum of the weights int initial_sum = 0; for (int i = 0; i < n; i++) { initial_sum += weights[i]; }

Step 9: Calculate the minimum sum of weights int min_sum = 0; for (int i = 0; i < k; i++) { min_sum += weights[i]; }

Step 10: Calculate the maximum sum of weights int max_sum = 0; for (int i = n - 1; i >= n - k; i--) { max_sum += weights[i]; }

Step 11: Calculate the difference between the maximum and minimum sum of weights int max_diff = max_sum - min_sum;

Step 12: Output the maximum weight difference cout << max_diff << endl;

Step 13: End the test cases loop }

Step 14: End the main function return 0; }

Explanation:

In this solution, we start by importing the necessary libraries, including iostream and algorithm. Then, we define the main function.

Next, we declare the variables t, n, and k. The variable t represents the number of test cases, n represents the number of children, and k represents the number of children to be selected.

Inside the main function, we start a loop to handle each test case. For each test case, we read the values of n and k from the input. We also declare an array to store the weights of the children.

We then read the weights of the children into the array using a loop. After that, we sort the array in ascending order using the sort() function from the algorithm library.

Next, we calculate the initial sum of the weights by iterating over the array and adding each weight to the initial_sum variable.

To find the minimum sum of weights, we iterate over the sorted array and add the first k elements to the min_sum variable.

Similarly, to find the maximum sum of weights, we iterate over the sorted array in reverse order and add the last k elements to the max_sum variable.

Finally, we calculate the difference between the maximum and minimum sum of weights and output it as the maximum weight difference.

The loop continues until all the test cases are processed, and then the main function ends.

I hope this explanation helps you understand the solution step by step. Let me know if you have any further questions.