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4048. Count Values With Equally Spaced Occurrences I

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4048. Count Values With Equally Spaced Occurrences I

Easy73.3% Acceptance

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:

  • 3 <= nums.length <= 100
  • 1 <= nums[i] <= 100

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[1,8,1,5,1,5,8,5]