Arrays: Left Rotation

Problem

A left rotation operation on an array shifts each of the array’s elements 1 unit to the left. For example, if 2 left rotations are performed on an array [1,2,3,4,5], then the array would become [3,4,5,1,2]. Note that the lowest index item move to the highest index in a rotation. This is called circular array.

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

Function Description

Complete the function rotLeft in the editor below.

rotLeft has the following parameter(s):

• int a[n]: the array to rotate
• int d: the number of rotations

Returns

• int a'[n]: the rotated array

Input Format

• The first line contains two space-separated integers n and d, the size of a and the number of left rotations.
• The second line contains n space-separated integers, each an a[i]

Constraints

• 1 <= n <= 105
• 1 <= d <= n
• 1 <= a[i] <=106

Sample Input

5 4
1 2 3 4 5

Output

5 1 2 3 4

When we perform d=4 left rotations, the array undergoes the following sequence of changes.

[1,2,3,4,5]->[2,3,4,5,1]->[3,4,5,1,2]->[4,5,1,2,3]->[5,1,2,3,4]

Solution:

package org.span;
import java.io.IOException;
public class ArrayLeftRotation {
    static int[] rotLeft(int[] a, int d) {
        for (int i = 0; i < d; i++) {
            int t = a[0];
            System.arraycopy(a, 1, a, 0, a.length - 1);
            a[a.length - 1] = t;
        }
        return a;
    }
    public static void main(String[] args) throws IOException {
        int d = 4;
        int[] a = {1, 2, 3, 4, 5};
        int[] result = rotLeft(a, d);
        print(result);
    }
    public static void print(int[] a) {
        for (int i = 0; i < a.length; i++) {
            if (i > 0)
                System.out.print(" " + a[i]);
            else
                System.out.print(a[i]);
        }
    }
}