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
#listlst = [23, 100, 54, 56, 98]#interchanging the first and last elementlst[0], lst[-1] = lst[-1], lst[0]print(lst)
Explanation
In the following code snippet:
- Line 2: We initialize
lstwith[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 withlst[-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 listint[] arr = {23, 100, 54, 56, 98};//temp variableint temp = arr[0];arr[0] = arr[arr.length-1];arr[arr.length-1] = temp;//printing modified arraySystem.out.println(Arrays.toString(arr));}}
Explanation
In the following code snippet:
- We initialize array
arrwith{23, 100, 54, 56, 98}. - We store the first element
arr[0]intemp. - Now, we assign the last element to the first element, and we get the last element by subtracting
1from the array length. - Now, we assign
tempto the last element.
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