Arrays: Left Rotation HackerRank Solution

Arrays: Left Rotation HackerRank Solution
Source : https://www.hackerrank.com/challenges/ctci-array-left-rotation

A left rotation operation on an array shifts each of the array's elements unit to the left. For example, if left rotations are performed on array , then the array would become .

Given an array of integers and a number, , perform left rotations on the array. Return the updated array to be printed as a single line of space-separated integers.

Function Description

Complete the function rotLeft in the editor below. It should return the resulting array of integers.

rotLeft has the following parameter(s):

• An array of integers .
• An integer , the number of rotations.

Input Format

The first line contains two space-separated integers and , the size of and the number of left rotations you must perform.
The second line contains space-separated integers .

Constraints

Output Format

Print a single line of space-separated integers denoting the final state of the array after performing left rotations.

Sample Input

5 41 2 3 4 5

Sample Output

5 1 2 3 4

Explanation

When we perform left rotations, the array undergoes the following sequence of changes:

Source : https://www.hackerrank.com/challenges/ctci-array-left-rotation

Solution

	// Karthikalapati.blogspot.com
	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;
	}
	}