Is Form Smallest Number From Two Digit Arrays easy or hard?

Form Smallest Number From Two Digit Arrays is classified as an Easy problem on LeetCode. The challenge focuses on recognizing that a shared digit forms the smallest possible number and applying a simple hash-based lookup to avoid unnecessary pair comparisons.

Form Smallest Number From Two Digit Arrays Python/Java solution

In Python or Java, the common solution builds a set or boolean array from the first list of digits and scans the second list to detect intersections. If a shared digit exists, return the smallest one; otherwise compute the minimal two-digit number from the smallest digits in both arrays.

How to solve Form Smallest Number From Two Digit Arrays in O(n)?

Store digits from the first array in a boolean array or hash set. While scanning the second array, check if any digit already exists in the set. If a match appears, track the smallest shared digit. If no match exists, compute the smallest digit in each array and combine them to form the minimal two-digit number.

What is the best approach for Form Smallest Number From Two Digit Arrays?

The best approach is the Intersection and Small Pair method. First detect whether the two arrays share a common digit using a hash set or small frequency array. If a common digit exists, return the smallest one. Otherwise combine the smallest digits from each array to form the smallest two‑digit number. This runs in O(n + m) time and O(1) space.

Is Form Smallest Number From Two Digit Arrays asked at Google/Amazon/Meta?

This problem represents a typical easy-level interview pattern involving arrays and hash lookups. Similar digit-combination and set-intersection questions appear in interviews at companies like Amazon, Google, and Meta to test basic data structure reasoning and edge-case handling.

What data structure is used in Form Smallest Number From Two Digit Arrays?

A hash table or boolean frequency array is commonly used to detect shared digits between the two arrays. Because digits are limited to 1–9, a fixed-size array of length 10 works efficiently and provides constant-time membership checks.

What is the time complexity of Form Smallest Number From Two Digit Arrays?

The optimal solution runs in O(n + m) time where n and m are the lengths of the two arrays. The algorithm scans each array once and performs constant-time lookups to check for intersections. Space complexity is O(1) because the digit range is limited to 1–9.

Description Hints 2 Solution Video 5:56

2605. Form Smallest Number From Two Digit Arrays

Easy55.1% acceptance1 company

Given two arrays of unique digits nums1 and nums2, return the smallest number that contains at least one digit from each array.

Example 1:

Input: nums1 = [4,1,3], nums2 = [5,7]
Output: 15
Explanation: The number 15 contains the digit 1 from nums1 and the digit 5 from nums2. It can be proven that 15 is the smallest number we can have.

Example 2:

Input: nums1 = [3,5,2,6], nums2 = [3,1,7]
Output: 3
Explanation: The number 3 contains the digit 3 which exists in both arrays.

Constraints:

1 <= nums1.length, nums2.length <= 9
1 <= nums1[i], nums2[i] <= 9
All digits in each array are unique.

Asked at 1 company

Tinkoff

Topics

Hints open one at a time

Hint 1

How many digits will the resulting number have at most?

Hint 2

The resulting number will have either one or two digits. Try to find when each case is possible.

5:56

Still stuck?Read 5 approaches, or watch a walkthrough.

Open solution

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

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

[4,1,3]
[5,7]

Input

[3,5,2,6]
[3,1,7]

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