Question

How to reverse the event indexes of an array in Java

Answer 1

import java.util.Arrays;
import java.util.Stack;

public class MyClass {
    public static void reverseEvenIndexes(int[] arr) {
        Stack<Integer> stack = new Stack<>();
        for (int i = 0; i < arr.length; i += 2) 
            stack.push(arr[i]);
        for (int i = 0; i < arr.length; i+= 2) 
            arr[i] = stack.pop();
    }
  
    public static void main(String args[]) {
        int[] arr = {3, -1, 8, -1, 4, -1, 7, -1};
        
        System.out.println(Arrays.toString(arr));
        
        reverseEvenIndexes(arr);
        
        System.out.println(Arrays.toString(arr));
    }
}



/*
run:

[3, -1, 8, -1, 4, -1, 7, -1]
[7, -1, 4, -1, 8, -1, 3, -1]

*/

 

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