Java Program to Find Range sum queries for anticlockwise rotations of Array by K indices

Given an array arr consisting of N elements and Q queries of the following two types:

1 K: For this type of query, the array needs to be rotated by K indices anticlockwise from its current state.
2 L R: For this query, the sum of the array elements present in the indices [L, R] needs to be calculated.

Example:

Input: arr = { 1, 2, 3, 4, 5, 6 }, query = { {2, 1, 3}, {1, 3}, {2, 0, 3}, {1, 4}, {2, 3, 5} }
Output:
9
16
12
Explanation:
For the 1st query {2, 1, 3} -> Sum of the elements in the indices [1, 3] = 2 + 3 + 4 = 9.
For the 2nd query {1, 3} -> Modified array after anti-clockwise rotation by 3 places is { 4, 5, 6, 1, 2, 3 }
For the 3rd query {2, 0, 3} -> Sum of the elements in the indices [0, 3] = 4 + 5 + 6 + 1 = 16.
For the 4th query {1, 4} -> Modified array after anti-clockwise rotation by 4 places is { 2, 3, 4, 5, 6, 1 }
For the 5th query {2, 3, 5} -> Sum of the elements in the indices [3, 5] = 5 + 6 + 1 = 12.

Approach:

Create a prefix array which is double the size of the arr and copy the element at the i^th index of arr to i^th and N + i^th index of prefix for all i in [0, N).
Precompute the prefix sum for every index of that array and store in prefix.
Set the pointer start at 0 to denote the starting index of the initial array.
For query of type 1, shift start to

((start + K) % N)^th position

For query of type 2, calculate

prefix[start + R]
 - prefix[start + L- 1 ]

if start + L >= 1 then print the value of

prefix[start + R]

Below code is the implementation of the above approach:

Java

// Java program to calculate range sum
// queries for anticlockwise
// rotations of array by K

class GFG{
 
// Function to execute the queries

static void rotatedSumQuery(int arr[], int n,

                            int [][]query, int Q)
{

    // Construct a new array

    // of size 2*N to store

    // prefix sum of every index

    int []prefix = new int[2 * n];
 
    // Copy elements to the new array

    for(int i = 0; i < n; i++)

    {

        prefix[i] = arr[i];

        prefix[i + n] = arr[i];

    }
 
    // Calculate the prefix sum

    // for every index

    for(int i = 1; i < 2 * n; i++)

        prefix[i] += prefix[i - 1];
 
    // Set start pointer as 0

    int start = 0;
 
    for(int q = 0; q < Q; q++)

    {
 
        // Query to perform

        // anticlockwise rotation

        if (query[q][0] == 1)

        {

            int k = query[q][1];

            start = (start + k) % n;

        }
 
        // Query to answer range sum

        else if (query[q][0] == 2) 

        {

            int L, R;

            L = query[q][1];

            R = query[q][2];
 
            // If pointing to 1st index

            if (start + L == 0)
 
                // Display the sum upto start + R

                System.out.print(prefix[start + R] + "
");
 
            else
 
                // Subtract sum upto start + L - 1

                // from sum upto start + R

                System.out.print(prefix[start + R] -

                                 prefix[start + L - 1] + 

                                 "
");

        }

    }
}
 
// Driver code

public static void main(String[] args)
{

    int arr[] = { 1, 2, 3, 4, 5, 6 };
 
    // Number of query

    int Q = 5;
 
    // Store all the queries

    int [][]query = { { 2, 1, 3 },

                      { 1, 3 },

                      { 2, 0, 3 },

                      { 1, 4 },

                      { 2, 3, 5 } };
 
    int n = arr.length;

    rotatedSumQuery(arr, n, query, Q);
}
}
 
// This code is contributed by Rohit_ranjan