How to interchange the first and last elements in a list

Problem

Given a list, swap the first and the last elements of the list.

Example

Input: [23, 100, 54, 56, 98]

Output: [98, 100, 54, 56, 23]

Python solution

We will use a Python feature to solve this which assigns multiple variables at the same time.

For example, if we have variables a and b, then we can assign values to it like this:

a,b = 10,20

Where:

10 is stored in a, and 20 is stored in b.

Code

#list

lst = [23, 100, 54, 56, 98]



#interchanging the first and last element

lst[0], lst[-1] = lst[-1], lst[0]



print(lst)

Explanation

In the following code snippet:

  • Line 2: We initialize lst with [23, 100, 54, 56, 98].
  • Line 5: We use the Python feature mentioned above to interchange the first and last elements in the list, with lst[0], lst[-1] = lst[-1], lst[0], where with lst[-1], we can access last element.
  • Line 7: We print the list where the first and last elements are interchanged.

Java solution

We will use a temporary variable to interchange the first and last elements in a list.

  • First, we will store the first element in a temporary variable.
  • Then, we assign the last element to the first element.
  • Lastly, we assign a temporary variable to the last element.

Code

import java.util.*;
class HelloWorld {
    public static void main( String args[] ) {
      //initialize the list
      int[] arr = {23, 100, 54, 56, 98};
      //temp variable
      int temp = arr[0];
      arr[0] = arr[arr.length-1];
      arr[arr.length-1] = temp;
      //printing modified array
      System.out.println(Arrays.toString(arr));
    }
}

Explanation

In the following code snippet:

  • We initialize array arr with {23, 100, 54, 56, 98}.
  • We store the first element arr[0] in temp.
  • Now, we assign the last element to the first element, and we get the last element by subtracting 1 from the array length.
  • Now, we assign temp to the last element.

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