Topic

Iterating over arrays

Problem

Right Rotation

A right rotation is an operation that shifts each element of an array to the right. For example, if an array is {1,2,3,4,5} and we right rotate it by 1, the new array will be {5,1,2,3,4}. If we rotate it by 2, the new array will be {4,5,1,2,3}. It goes like this: {1,2,3,4,5} -> {5,1,2,3,4} -> {4,5,1,2,3}.

Write a program that performs a right rotation on an array by a given number.

Note that If your solution gets the code quality warning "System.arraycopy is more efficient", please simply ignore it in respect of this code challenge.

Input format: The first line is an array of numbers. The second line is the number of rotations.

Output format: Resulting array

Sample Input 1:

1 2 3 4 5
1

Sample Output 1:

5 1 2 3 4

Sample Input 2:

1 2 3 4 5
2

Sample Output 2:

4 5 1 2 3

Sample Input 3:

1 2 3 4 5
8

Sample Output 3:

3 4 5 1 2

Sample Input 4:

11 21 1 41 51 78 90
4

Sample Output 4:

41 51 78 90 11 21 1

Hint & Explain

You can create array of Strings in this way: String[] entrance = scanner.nextLine().split(" "); Spaces will be to divide each element of array.

Leetcode题解 - 旋转数组 (opens new window)

Solution

My solution

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        // put your code here
        Scanner scanner = new Scanner(System.in);
        String[] array = scanner.nextLine().split(" ");
        int times = scanner.nextInt();
        String before;
        String after = array[0];

        for (int j = 1; j <= times; j++) {
            array[0] = array[array.length - 1];
            for (int i = 0; i < array.length; i++) {
                if (i + 1 < array.length) {
                    before = after;
                    after = array[i + 1];
                    array[i + 1] = before;
                }
            }
        }

        for (String item :
                array) {
            System.out.print(item + " ");
        }
    }
}

Other solution 1

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String[] array = scanner.nextLine().split(" ");
        int arrayShift = scanner.nextInt() % array.length;
        String[] newArray = new String[array.length];

        for (int i = 0; i < newArray.length; i++) {
            int index = (arrayShift + i) % array.length;
            newArray[index] = array[i];
        }

        for (String element : newArray) {
            System.out.print(element + " ");
        }
    }
}

Other solution 2

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        int step = scanner.nextInt();
        String[] row = s.split(" ");
        int len = row.length;
        int remember = step % len;

        String temp;

        for (int j = 0; j < remember; j++) {
            temp = row[len - 1];
            System.arraycopy(row, 0, row, 1, len - 2 + 1);
            row[0] = temp;
        }
        String str = String.join(" ", row);
        System.out.println(str);
    }
}

Other solution 3

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        ArrayList<Integer> list = new ArrayList<>();

        String[] array = scanner.nextLine().split(" ");
        int value = scanner.nextInt();

        for (String string : array) {
            int num = Integer.parseInt(string);
            list.add(num);
        }

        Collections.rotate(list, value);

        for (Integer num : list) {
            System.out.print(num + " ");
        }
    }
}