reverse arraylist java recursion
public ArrayList<Object> reverse(ArrayList<Object> arrayList) {
if(arrayList.size() > 1) {
Object value = arrayList.remove(0);
reverse(arrayList);
arrayList.add(value);
}
return arrayList;
}how to reverse an arraylist in java using recursion
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/*
* Java Program to demonstrate how to reverse a List.
* In this example, you will see two ways to reverse a List,
* first, using Collections.reverse() method and second
* by writing your own method using recursion.
*/
public class TestSolution {
public static void main(String args[]) {
List<String> books = new ArrayList<>();
books.add("Beautiful Code");
books.add("Clean Code");
books.add("Working Effectively with Legacy Code");
System.out.println("Original order of List: " + books);
// Easy way to reverse a List in Java, use Collections.reverse()
// method, use this to reverse ArrayList or LinkedList in
// production
Collections.reverse(books);
System.out.println("The reversed List: " + books);
// Now, let's try to reverse a List using recursion
List<String> output = reverseListRecursively(books);
System.out.println("Reversed list reversed again: " + output);
}
/**
* A recursive algorithm to reverse a List in Java
*
* @param list
* @return
*/
private static List<String> reverseListRecursively(List<String> list) {
if (list.size() <= 1) {
return list;
}
List<String> reversed = new ArrayList<>();
reversed.add(list.get(list.size() - 1)); // last element
reversed.addAll(reverseListRecursively(list.subList(0, list.size() - 1)));
return reversed;
}
}
Output
Original order of List: [Beautiful Code, Clean Code, Working Effectively with Legacy Code]
The reversed List: [Working Effectively with Legacy Code, Clean Code, Beautiful Code]
Reversed list reversed again: [Beautiful Code, Clean Code, Working Effectively with Legacy Code]Copyright © 2021 Codeinu
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