Is Two Out of Three easy or hard?

Two Out of Three is classified as an Easy problem. The challenge mainly tests understanding of sets, hash tables, and duplicate handling. Once you recognize that duplicates inside the same array must be ignored, the solution becomes straightforward.

How to solve Two Out of Three in O(n)?

Use three sets to remove duplicates from each array. Track element presence using a hash map or frequency array. Increment the count for each number appearing in a set, and collect numbers with a count of at least two. Since every element is processed once, the total runtime is linear.

What is the best approach for Two Out of Three?

The most practical approach uses sets combined with a hash map. Convert each array into a set to remove duplicates, then count how many arrays contain each value. Any number appearing in at least two sets is added to the result. This runs in O(n + m + k) time with hash lookups.

Is Two Out of Three asked at Google/Amazon/Meta?

Problems involving set intersections and hash-based counting frequently appear in interviews at companies like Amazon and Meta. While this exact question may vary, the pattern of deduplicating arrays and counting occurrences across collections is common in coding interviews.

What data structure is used in Two Out of Three?

The primary data structures are hash sets and hash maps. Sets ensure duplicates inside a single array are ignored, while a hash map tracks how many arrays contain each value. Some implementations replace the map with a frequency array when the number range is limited.

What is the time complexity of Two Out of Three?

The optimal solution runs in O(n + m + k) time, where n, m, and k are the lengths of the three arrays. Each array is processed once to build sets and update counts. Hash map operations are O(1) on average, keeping the overall complexity linear.

Two Out of Three Python or Java solution approach?

Both Python and Java implementations typically convert arrays into sets and use a dictionary or HashMap to count occurrences. Iterate through each set and increment the count for its elements. Finally, return all numbers whose count is at least two.

Description Hints 2 Solution Video 3:00

2032. Two Out of Three

Easy77.5% acceptance2 companies

Given three integer arrays nums1, nums2, and nums3, return a distinct array containing all the values that are present in at least two out of the three arrays. You may return the values in any order.

Example 1:

Input: nums1 = [1,1,3,2], nums2 = [2,3], nums3 = [3]
Output: [3,2]
Explanation: The values that are present in at least two arrays are:
- 3, in all three arrays.
- 2, in nums1 and nums2.

Example 2:

Input: nums1 = [3,1], nums2 = [2,3], nums3 = [1,2]
Output: [2,3,1]
Explanation: The values that are present in at least two arrays are:
- 2, in nums2 and nums3.
- 3, in nums1 and nums2.
- 1, in nums1 and nums3.

Example 3:

Input: nums1 = [1,2,2], nums2 = [4,3,3], nums3 = [5]
Output: []
Explanation: No value is present in at least two arrays.

Constraints:

1 <= nums1.length, nums2.length, nums3.length <= 100
1 <= nums1[i], nums2[j], nums3[k] <= 100

Asked at 2 companies

Booking.com Info Edge

Topics

Hints open one at a time

Hint 1

What data structure can we use to help us quickly find whether an element belongs in an array?

Hint 2

Can we count the frequencies of the elements in each array?

3:00

Still stuck?Read 3 approaches, or watch a walkthrough.

Open solution

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1class Solution:
2    def twoOutOfThree(self, nums1: List[int], nums2: List[int], nums3: List[int]) -> List[int]:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2Case 3

Input

[1,1,3,2]
[2,3]
[3]

Input

[3,1]
[2,3]
[1,2]

Input

[1,2,2]
[4,3,3]
[5]

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