Array Reversal Techniques in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to reverse the array using slicing.

DSA Python

arr = [1, 2, 3, 4, 5]
reversed_arr = arr[1]
print(reversed_arr)

Drag options to blanks, or click blank then click option'

A[:]

B[1:]

C[::-1]

D[::-2]

Attempts:

3 left

💡 Hint

Common Mistakes

Using [:] which copies the list but does not reverse it.

Using [1:] which slices from the second element onward.

Using [::-2] which skips elements while reversing.

Using [::-1] reverses the list by slicing it from end to start.

2fill in blank

medium

Complete the code to reverse the array using the built-in reverse() method.

DSA Python

arr = [10, 20, 30, 40]
arr.[1]()
print(arr)

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Areverse

Bflip

Cinvert

Drevert

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods like flip or invert which do not exist.

Trying to assign the result of reverse() which returns None.

The reverse() method reverses the list in place.

3fill in blank

hard

Fix the error in the code to reverse the array using a for loop.

DSA Python

arr = [5, 6, 7, 8]
reversed_arr = []
for i in range(len(arr)[1]):
    reversed_arr.append(arr[i])
print(reversed_arr)

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A1, 0, -1

B-1, -1, -1

C0, -1, 1

D-1, 0, -1

Attempts:

3 left

💡 Hint

Common Mistakes

Using positive step which causes an empty loop.

Incorrect start or stop values causing index errors.

The range should start from the last index len(arr)-1 down to -1 stepping by -1 to reverse the list.

4fill in blank

hard

Fill the blank to reverse the array using swapping elements in place.

DSA Python

arr = [9, 8, 7, 6]
n = len(arr)
for i in range(n[1]):
    arr[i], arr[n - 1 - i] = arr[n - 1 - i], arr[i]
print(arr)

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A//2

B-//2

C-2

D/2

Attempts:

3 left

💡 Hint

Common Mistakes

Using float division which causes errors.

Looping over the entire list causing double swaps.

The range(n//2) iterates over the first half of the array. Swapping arr[i] with arr[n-1-i] reverses the array in place.

5fill in blank

hard

Fill all three blanks to create a reversed copy of the array using list comprehension.

DSA Python

arr = [3, 4, 5, 6]
reversed_arr = [arr[[1]] for [2] in range(len(arr)) if [3] < len(arr)]
print(reversed_arr)

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Alen(arr) - 1 - i

Bi

Dlen(arr)

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable for the index.

Missing or incorrect condition causing index errors.

The index is reversed by subtracting i from len(arr) - 1. The variable i iterates over the range. The condition i < len(arr) ensures valid indices.