4048. Count Values With Equally Spaced Occurrences I - Solution & Explanation

Problem Statement

You are given an integer array nums.

An integer x is called special if:

x appears exactly three times in nums.
All three occurrences of x are equally spaced in nums. In other words, if all occurrences of x are at indices i₁ < i₂ < i₃, then i₂ - i₁ = i₃ - i₂.

Return the number of distinct special integers in nums.

Example 1:

Input: nums = [1,8,1,5,1,5,8,5]

Output: 2

Explanation:

1 is special because it occurs exactly three times at equally spaced indices 0, 2, and 4.
5 is special because it occurs exactly three times at equally spaced indices 3, 5, and 7.
8 is not special because it occurs only twice.

Therefore, the answer is 2.

Example 2:

Input: nums = [8,8,8,8]

Output: 0

Explanation:

8 is not special because it does not occur exactly three times. Therefore, the answer is 0.

Example 3:

Input: nums = [8,6,6,8,8]

Output: 0

Explanation:

8 occurs at indices 0, 3, and 4, which are not equally spaced. 6 occurs only twice. Therefore, no integer is special.

Constraints:

Solutions for this problem are being prepared.

LeetCode 4048: Count Values With Equally Spaced Occurrences I | Easy HashMap Solution! • engfootsteps • 13 views views