Example: Left Array Rotation using Temporary Array in Java

// Left Array Rotation using Temporary Array
import java.util.Arrays; // Required for Arrays.toString()

// Main class containing the entry point of the program
public class Main {
    /**
     * Performs a left rotation on an array by 'd' positions.
     *
     * @param arr The array to be rotated.
     * @param d The number of positions to rotate left.
     */
    static void leftRotate(int[] arr, int d) {
        // Handle edge cases: null array or empty array
        if (arr == null || arr.length == 0) {
            return;
        }
        int n = arr.length;
        // Adjust d to be within array bounds (in case d >= n)
        // A rotation by n is equivalent to no rotation.
        d = d % n;

        // Step 1: Create a temporary array to store the first d elements
        int[] temp = new int[d];
        for (int i = 0; i < d; i++) {
            temp[i] = arr[i];
        }

        // Step 2: Shift the remaining elements (from index d to n-1) to the left
        // These elements move to positions (i - d)
        for (int i = d; i < n; i++) {
            arr[i - d] = arr[i];
        }

        // Step 3: Copy the elements from the temporary array to the end of the original array
        // These elements go into positions (n - d + i)
        for (int i = 0; i < d; i++) {
            arr[n - d + i] = temp[i];
        }
    }

    public static void main(String[] args) {
        // Example 1
        int[] arr1 = {1, 2, 3, 4, 5, 6, 7};
        int d1 = 2; // Number of positions to rotate left

        System.out.println("Original Array: " + Arrays.toString(arr1));
        leftRotate(arr1, d1); // Perform left rotation
        System.out.println("Array after " + d1 + " left rotations: " + Arrays.toString(arr1));

        System.out.println("-------------------------------------");

        // Example 2
        int[] arr2 = {10, 20, 30, 40, 50};
        int d2 = 3;
        System.out.println("Original Array: " + Arrays.toString(arr2));
        leftRotate(arr2, d2);
        System.out.println("Array after " + d2 + " left rotations: " + Arrays.toString(arr2));
    }
}