HackerRank Solutions – Arrays – Left Rotation – Java Solution
All credits to Rodney Shaghoulian for this simple solution for the HackerRank challenge – Arrays – Left Rotation. This solution is written in Java.
// Author: Rodney Shaghoulian // Github: github.com/RodneyShag import java.util.Scanner; // Time Complexity: O(n) // Space Complexity: O(1) by doing an "in place" rotation public class Solution { public static void main(String[] args) { /* Save input */ Scanner scan = new Scanner(System.in); int size = scan.nextInt(); int numRotations = scan.nextInt(); int array[] = new int[size]; for (int i = 0; i < size; i++) { array[i] = scan.nextInt(); } scan.close(); /* Rotate array (in place) using 3 reverse operations */ numRotations %= size; // to account for numRotations > size int rotationSpot = size - 1 - numRotations; reverse(array, 0, size - 1); reverse(array, 0, rotationSpot); reverse(array, rotationSpot + 1, size - 1); /* Print rotated array */ for (int i = 0; i < size; i++) { System.out.print(array[i] + " "); } } /* Reverses array from "start" to "end" inclusive */ private static void reverse(int[] array, int start, int end) { if (array == null || start < 0 || start >= array.length || end < 0 || end >= array.length) { return; } while (start < end) { swap(array, start++, end--); } } private static void swap(int [] array, int i, int j) { int temp = array[i]; array[i] = array[j]; array[j] = temp; } }