Reverse An Array - 3 Methods

• Method 1 - Revere with For Loop and print

public class ReverseArray {
public static void main(String[] args) {
// Array with some element
int[] myArray = {10,22,33,11,88,9,2};
    // reverse loop and printing
    for(int i = myArray.length-1;i>=0;i--) {
        System.out.print(myArray[i]+ " ");
        }
    }
}

• Method 2 - Using Array List

// Method 2 Reverse an array using array list
    public class ReverseArray {
    public static void main(String[] args) {
        // Array List
        ArrayList<Integer> myArray = new ArrayList<Integer>();
        myArray.add(10);
        myArray.add(21);
        myArray.add(13);
        myArray.add(14);
        myArray.add(51);

        // reverse array and method
        Collections.reverse(myArray);
        System.out.println(myArray);
    }
}

• Method 3 - Two Pointers and Swap

// Method 3 Reverse with swap
public class ReverseArray {
public static void main(String[] args) {

    // Array with some element
    int[] myArray = {10,22,33,11,88,9,2};

    int start = 0;
    int end = myArray.length-1;
    int temp = 0;

    // looping and swapping
    while(end>start) {
        temp = myArray[start];
        myArray[start] = myArray[end];
        myArray[end] = temp;
        end--;
        start++;
    }

    for(int i:myArray) {
        System.out.print(i+" ");
    }
}
}

Comments

[Alex Lohr]

This seems to be C++, not JavaScript. In JavaScript, you'd have

const myArray = [10,22,33,11,88,9,2]

// native (will change the original reference)
myArray.reverse()
console.log(myArray)

myArray.reverse() // change it back

// functional
const functionalReversedMyArray = myArray.reduce((result, item) => [item, ...result], [])
console.log(functionalReversedMyArray)

// imperative
const imperativeReversedMyArray = []
for (const index in myArray) {
  imperativeReversedMyArray.unshift(myArray[index])
}
console.log(imperativeReversedMyArray)

// recursive
const recursiveArrayReversal = (inputArray, partiallyReversed = []) => 
  inputArray.length
  ? recursiveArrayReversal(inputArray.slice(1), [inputArray[0], ...partiallyReversed])
  : partiallyReversed
const recursiveReversedMyArray = recursiveArrayReversal(myArray)
console.log(recursiveReversedMyArray)

[Amritanshu Dev Rawat]

Thanks :) That was JAVA :)

[Davis Tibbz]

Here is a crazy one 😀:

public static int[] reverse(int[] array) {
       return IntStream.range(0, array.length).map(i -> array[array.length - 1 - i]).toArray();
    }
 public static void main(String[] args) {
    //integer array 'a'
     var a = reverse(new int[]{2, 4, 5, 6, 7, 8});
    System.out.println(Arrays.toString(a));
    }

[June July]

Great work bro!

[Amritanshu Dev Rawat]

:) thanks