Read a list of n elements. Pass this list to a function which reverses this list in-place without creating a new list.

Read a list of $\mathrm{n}$ elements. Pass this list to a function which reverses this list in-place without creating a new list.

Here is a program that reads a list of ( n ) elements and passes it to a function that reverses the list in place without creating a new list:

# Function to reverse the list in place
def reverse_list_in_place(lst):
    left = 0
    right = len(lst) - 1
    while left < right:
        # Swap the elements at positions left and right
        lst[left], lst[right] = lst[right], lst[left]
        left += 1
        right -= 1

# Read the number of elements
n = int(input("Enter the number of elements in the list: "))

# Read the list elements
lst = []
for i in range(n):
    element = int(input(f"Enter element {i+1}: "))
    lst.append(element)

print("Original list:", lst)

# Reverse the list in place
reverse_list_in_place(lst)

print("Reversed list:", lst)

Explanation

• Function reverse_list_in_place(lst):

  • It takes a list lst.

  • Two pointers left and right are initialized to the start and end of the list.

  • Elements are swapped while left is less than right, and pointers are moved closer to each other.

• Reading input:

  • The user is prompted to enter the number of elements (n).

  • A loop is used to read n elements from the user and append them to the list lst.

• Displaying results:

  • The original list is displayed.

  • The list is passed to reverse_list_in_place(lst) to reverse it.

  • The reversed list is displayed.

This ensures that the list is reversed in-place without creating a new list.