Arrays: Left Rotation

A left rotation operation on an array of size  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. Then print the updated array as a single line of space-separated integers.

Input Format

The first line contains two space-separated integers denoting the respective values of  (the number of integers) and  (the number of left rotations you must perform). 
The second line contains  space-separated integers describing the respective elements of the array's initial state.

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 4
1 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:

Thus, we print the array's final state as a single line of space-separated values, which is 5 1 2 3 4.

최근 풀이

index 에 대해 고민해보고 풀어봤다.

rotation과 관련한 문제를 풀 때는 전체 index와 옮겨지는index의 차이 및 합이

array의 length를 넘어가는 경우 재배치해주식으로 하면 쉽게 풀 수 있는 거 같다.

package datastructure;

import java.util.Scanner;

public class LeftRotation {

    public static int[] arrayLeftRotation(int[] a, int n, int k) {
        int[] results = new int[n];
        for (int i = 0; i < n; i++){
            if (i-k < 0){
                results[n + (i-k)] = a[i];

            } else {
                results[i-k] = a[i];
            }
        }
        return results;
    }


    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 a_i = 0; a_i < n; a_i++) {
            a[a_i] = in.nextInt();
        }

        int[] output = new int[n];
        output = arrayLeftRotation(a, n, k);
        for (int i = 0; i < n; i++)
            System.out.print(output[i] + " ");

        System.out.println();

    }
}

풀이

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 a_i=0; a_i < n; a_i++){

            a[a_i] = in.nextInt();

        }

        int[] copy = new int[n];

        System.arraycopy(a, k, copy, 0, n-k);

        System.arraycopy(a, 0, copy, n-k, k);

        System.out.println(Arrays.toString(copy).replace("[", "").replace("]", "").replace(",", ""));

    }

}

arraycopy 에 대한참고자료

http://forum.falinux.com/zbxe/index.php?document_srl=571358&mid=lecture_tip