Reverse an array or string

Given an array (or string), the task is to reverse the array/string.

Examples :

Input : arr[] = {1, 2, 3}

Output : arr[] = {3, 2, 1}

Input : arr[] = {4, 5, 1, 2}

Output : arr[] = {2, 1, 5, 4}

Iterative way :

1. Initialize start and end indexes as start = 0, end = n-1

2. In a loop, swap arr[start] with arr[end] and change start and end as follows :

start = start +1, end = end – 1

1 2 3 4 5 6

Reversed array is

6 5 4 3 2 1

Time Complexity : O(n)

Recursive Way :

1. Initialize start and end indexes as start = 0, end = n-1

2. Swap arr[start] with arr[end]

3. Recursively call reverse for rest of the array.

Output :

1 2 3 4 5 6

Reversed array is

6 5 4 3 2 1

Time Complexity : O(n)