Three Sum Problem All Unique Triplets in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sort the input list before processing.

DSA Python

nums = [3, 0, -2, -1, 1, 2]
nums.[1]()

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

Areverse

Bsorted

Csort

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using sorted() which returns a new list but does not change the original list.

Using reverse() which only reverses the list order.

We use the sort() method to sort the list in place before finding triplets.

2fill in blank

medium

Complete the code to skip duplicate elements for the first pointer in the triplet search.

DSA Python

for i in range(len(nums)):
    if i > 0 and nums[i] == nums[1]:
        continue

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

A-1

Bi+1

C0

Di-1

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing with the next element instead of the previous.

Using an invalid index like 0 or -1 incorrectly.

We compare the current element with the previous one to skip duplicates.

3fill in blank

hard

Fix the error in the while loop condition to correctly move the left pointer.

DSA Python

while left < right and nums[left] == nums[1]:
    left += 1

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Aleft-1

Bleft+1

Cright-1

Dright+1

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing with the next element which may cause index errors.

Using right pointer indices incorrectly.

We compare the current left element with the previous left element to skip duplicates.

4fill in blank

hard

Fill both blanks to correctly move the right pointer and skip duplicates after finding a valid triplet.

DSA Python

while left < right and nums[right] == nums[1]:
    right = [2]

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Aright+1

Bright-1

Cleft+1

Dleft-1

Attempts:

3 left

💡 Hint

Common Mistakes

Increasing the right pointer which goes out of bounds.

Comparing with left pointer indices.

We compare the current right element with the previous right element and move the right pointer leftwards to skip duplicates.

5fill in blank

hard

Fill all three blanks to complete the dictionary comprehension that counts the frequency of each number in the list.

DSA Python

count = [1](num: nums.count(num) for num in [2])
unique_nums = sorted(count.[3]())

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

Adict

Bnums

Ckeys

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using list instead of dict for the comprehension.

Iterating over dictionary keys instead of the original list.

Using values() instead of keys().

We use dict to create a dictionary, iterate over nums, and get the keys from the dictionary to sort unique numbers.