Is Assign Elements to Groups with Constraints easy or hard?

Assign Elements to Groups with Constraints is rated Medium difficulty. The brute-force logic is simple, but optimizing it requires recognizing repeated constraint checks and applying a hash table to avoid nested loops.

Assign Elements to Groups with Constraints Python/Java solution

A typical Python or Java solution iterates through groups and checks candidate elements using a dictionary or HashMap. The map stores elements by the constraint key so each group can quickly find a valid assignment. The optimized implementation runs in roughly O(n + m) time.

How to solve Assign Elements to Groups with Constraints in O(n)?

Achieving near O(n) performance requires preprocessing elements into a hash table. Each element is inserted once, and each group performs constant-time lookups to find a valid candidate instead of scanning the entire list. This removes the nested loop and reduces the total work to linear passes over the input.

What is the best approach for Assign Elements to Groups with Constraints?

The most effective approach uses enumeration combined with a hash table. Preprocess elements into a hash map keyed by the property used in the constraint, then iterate through groups and perform constant-time lookups. This reduces repeated scanning and typically runs in O(n + m) time with O(m) extra space.

Is Assign Elements to Groups with Constraints asked at Google/Amazon/Meta?

Problems involving constrained assignment, hashing, and array processing frequently appear in interviews at companies like Amazon, Google, and Meta. Variants of this question test your ability to reduce brute-force enumeration using hash maps or other indexing structures.

What data structure is used in Assign Elements to Groups with Constraints?

Arrays store the groups and elements, while a hash table is typically used to index elements by the attribute used in the constraint. The hash map allows constant-time lookups, which eliminates repeated scanning across the elements array.

What is the time complexity of Assign Elements to Groups with Constraints?

The brute force solution runs in O(n * m) time because each group may scan all elements. With a hash table optimization that indexes elements by the relevant constraint property, the complexity improves to about O(n + m) on average with O(m) auxiliary space.

Description Hints 4 Solution Video 11:39

3447. Assign Elements to Groups with Constraints

Medium27.4% acceptance1 company

You are given an integer array groups, where groups[i] represents the size of the i^th group. You are also given an integer array elements.

Your task is to assign one element to each group based on the following rules:

An element at index j can be assigned to a group i if groups[i] is divisible by elements[j].
If there are multiple elements that can be assigned, assign the element with the smallest index j.
If no element satisfies the condition for a group, assign -1 to that group.

Return an integer array assigned, where assigned[i] is the index of the element chosen for group i, or -1 if no suitable element exists.

Note: An element may be assigned to more than one group.

Example 1:

Input: groups = [8,4,3,2,4], elements = [4,2]

Output: [0,0,-1,1,0]

Explanation:

elements[0] = 4 is assigned to groups 0, 1, and 4.
elements[1] = 2 is assigned to group 3.
Group 2 cannot be assigned any element.

Example 2:

Input: groups = [2,3,5,7], elements = [5,3,3]

Output: [-1,1,0,-1]

Explanation:

elements[1] = 3 is assigned to group 1.
elements[0] = 5 is assigned to group 2.
Groups 0 and 3 cannot be assigned any element.

Example 3:

Input: groups = [10,21,30,41], elements = [2,1]

Output: [0,1,0,1]

Explanation:

elements[0] = 2 is assigned to the groups with even values, and elements[1] = 1 is assigned to the groups with odd values.

Constraints:

1 <= groups.length <= 10⁵
1 <= elements.length <= 10⁵
1 <= groups[i] <= 10⁵
1 <= elements[i] <= 10⁵

Asked at 1 company

Bcg

Topics

Array Hash Table

Hints open one at a time

Hint 1

Can a sieve-like approach be applied here?

Hint 2

Starting from the smallest index, iterate through the multiples of the element and assign it to groups divisible by that value.

Hint 3

Process each element once.

Hint 4

Find all divisors of each group, then match them with elements.

11:39

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1class Solution:
2    def assignElements(self, groups: List[int], elements: List[int]) -> List[int]:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2Case 3

Input

[8,4,3,2,4]
[4,2]

Input

[2,3,5,7]
[5,3,3]

Input

[10,21,30,41]
[2,1]

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