Is Degree of an Array easy or hard?

Degree of an Array is classified as an Easy problem on LeetCode with an acceptance rate above 50%. The challenge is recognizing that you must track both frequency and index range to compute the smallest valid subarray.

How to solve Degree of an Array in O(n)?

Traverse the array and store three values for each number: frequency, first index, and last index. Track the maximum frequency (the degree). For numbers with that frequency, compute the subarray length using lastIndex - firstIndex + 1 and return the minimum length found.

What is the best approach for Degree of an Array?

The best approach uses a hash map to track each element's frequency along with its first and last occurrence indices. After computing the array's degree, calculate the smallest subarray length for elements that reach that degree using lastIndex - firstIndex + 1. This runs in O(n) time with O(n) space.

Is Degree of an Array asked at Google/Amazon/Meta?

Degree of an Array appears in coding interviews at several large tech companies including Amazon and other FAANG-level companies. The problem tests understanding of hash maps, frequency counting, and identifying minimal subarrays.

What data structure is used in Degree of an Array?

The main data structure is a hash table (hash map). It stores frequencies and indices for each number, allowing constant-time updates and lookups while scanning the array.

What is the time complexity of Degree of an Array?

The optimal solution runs in O(n) time because the array is traversed once (or twice) and each operation on the hash map is O(1) on average. Space complexity is O(n) in the worst case when all elements are unique.

Degree of an Array Python or Java solution approach?

In both Python and Java, the solution typically uses a dictionary or HashMap to store frequency counts and the first and last positions of each element. After computing the degree, iterate through the map to find the smallest subarray that maintains that degree.

Description Hints 1 Solution Video 12:06

697. Degree of an Array

Easy58.8% acceptance12 companies

Given a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of any one of its elements.

Your task is to find the smallest possible length of a (contiguous) subarray of nums, that has the same degree as nums.

Example 1:

Input: nums = [1,2,2,3,1]
Output: 2
Explanation: 
The input array has a degree of 2 because both elements 1 and 2 appear twice.
Of the subarrays that have the same degree:
[1, 2, 2, 3, 1], [1, 2, 2, 3], [2, 2, 3, 1], [1, 2, 2], [2, 2, 3], [2, 2]
The shortest length is 2. So return 2.

Example 2:

Input: nums = [1,2,2,3,1,4,2]
Output: 6
Explanation: 
The degree is 3 because the element 2 is repeated 3 times.
So [2,2,3,1,4,2] is the shortest subarray, therefore returning 6.

Constraints: