Hackerrank: Cracking the Coding Interview – Arrays: Left Rotation

The solution is easy if you know how the mod operator works. You take every original index and shift it to the left by d. This, however, can lead to negative values so we increment this value by the size of the array (n) and mod it by n so that all values fit within [0, n – 1]. You can also think of this as adding (n-k) to every index if that makes more sense.

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

Solution:

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int k = in.nextInt();
        int a[] = new int[n];
        for(int i=0; i < n; i++){
            a[(i - k + n) % n] = in.nextInt();
        }
        for (int i=0; i<n; i++) {
            System.out.print(a[i]);
            System.out.print(" ");
        }
    }
}

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