Challenge: Reverse in Place

Lab Python Beginner 10 points

Read a list of words and reverse it in place using two positions that move towards each other and swap (no reverse(), no slicing, no new list). Print the words separated by spaces.

Input

One line of words.

Output

The words in reverse order.

Example

Input

one two three four

Output

four three two one

Sample input available Sample output available

Editor

Python

Hints

Start left at 0 and right at the last index.

Swap, then move left forward and right backward, until they meet.

Solution explanation

About n/2 swaps: O(n) time, and only two extra variables: O(1) space.

Show solution

words = input().split()
left, right = 0, len(words) - 1
while left < right:
    words[left], words[right] = words[right], words[left]
    left += 1
    right -= 1
print(" ".join(words))

Output

Answer