Python Program to Display Array Elements in Reverse Order

Python programs to display array elements in reverse order have been shown here. Both of the iterative and recursive approaches have been covered. The algorithm, pseudocode and time complexity of the programs have also been given.

Example:

Given array A[] = {10, 20, 30, 40}

Elements of A[] in reverse order = {40, 30, 20, 10}

In Python, we can also reverse an array using the reverse() method or the [::-1] slicing syntax.

Page content(s):

1. Algorithm

2. Pseudocode

3. Time Complexity

4. Program & output

 4.1. Iterative approach

 4.2. Recursive approach

 4.3. Using reverse() method

 4.4. Using slicing [::-1]

1. Algorithm to display array elements in reverse order

1. Take input of an array $A[~]$ and the size $n$

2. Set $i = n - 1$

3. For each $i$ from $n - 1$ to $0$, dislay $A[i]$

2. Pseudocode to display array elements in reverse order

Input: An array $A[~]$ and size of array $n$

Output: Array elements in reverse order.

1. Procedure reverse($A[~]$, $n$):

2. Repeat for $i \in [n-1, 0]$:

3. Print $A[i]$

4. End Procedure

3. Time complexity to display array elements in reverse order

Time Complexity: O(n)

Here $n$ is the number of elements in the array.

4. Program & output to display array elements in reverse order

4.1. Python Program & output to display array elements in reverse order using iterative approach

Code has been copied

# ********************************************
#           alphabetacoder.com
#   Python program to print elements of array
#       in reverse order using iteration
# ********************************************

# declare an array
arr = [10, 20, 30, 40, 50, 60, 70, 80]

# display the array
print("Original array:", arr)

# display array elements in reverse order
print("Reverse array : ", end="")
for i in range(len(arr) - 1, -1, -1):
    print(arr[i], end=" ")

Output

Original array: [10, 20, 30, 40, 50, 60, 70, 80]

Reverse array : 80 70 60 50 40 30 20 10

4.2. Python Program to display array elements in reverse order using recursion

Code has been copied

# ********************************************
#           alphabetacoder.com
#   Python program to print elements of array
#       in reverse order using recursion
# ********************************************

# display elements of array in reverse
# order function takes an array arr and
# an index i as arguments
def reverse(arr, i):
    # exit condition of recursive call
    if i < 0:
        return
    # print current element
    print(arr[i], end=" ")
    # call function
    reverse(arr, i - 1)


def main():
    # declare an array
    arr = [10, 20, 30, 40, 50, 60, 70, 80]
    # display original array
    print("Original array:", arr)
    # call function to display array in reverse
    print("Reverse array: ", end="")
    reverse(arr, len(arr) - 1)


# driver code
main()

4.3. Python Program to display array elements in reverse order using reverse() method

Code has been copied

# ********************************************
#           alphabetacoder.com
#  Python program to print elements of array
#   in reverse order using reverse() method
# ********************************************

# declare an array
arr = [10, 20, 30, 40, 50, 60, 70, 80]
# display the array
print("Original array:", arr)

# reverse the array using reverse() mthod
arr.reverse()

# display reversed array
print("Reverse array:", arr)

4.4. Python Program to display array elements in reverse order using Using slicing [::-1]

Code has been copied

# ********************************************
#           alphabetacoder.com
#  Python program to print elements of array
#  in reverse order using slicing [::-1]
# ********************************************

# declare an array
arr = [10, 20, 30, 40, 50, 60, 70, 80]
# display the array
print("Original array:", arr)

# display reversed array using slicing [::-1]
print("Reverse array:", arr[::-1])