Subsequences with a Unique Middle Mode I
Given an integer array nums, find the number of subsequences of size 5 of nums with a unique middle mode.
Given an integer array nums, find the number of subsequences of size 5 of nums with a unique middle mode.
Since the answer may be very large, return it modulo 10^9 + 7.
A mode of a sequence of numbers is defined as the element that appears the maximum number of times in the sequence.
A sequence of numbers contains a unique mode if it has only one mode.
A sequence of numbers seq of size 5 contains a unique middle mode if the middle element (seq[2]) is a unique mode.
Example 1
Input: nums = [1,1,1,1,1,1]
Output: 6
Explanation: [1, 1, 1, 1, 1] is the only subsequence of size 5 that can be formed, and it has a unique middle mode of 1. This subsequence can be formed in 6 different ways, so the output is 6.
Example 2
Input: nums = [1,2,2,3,3,4]
Output: 4
Explanation: [1, 2, 2, 3, 4] and [1, 2, 3, 3, 4] each have a unique middle mode because the number at index 2 has the greatest frequency in the subsequence. [1, 2, 2, 3, 3] does not have a unique middle mode because 2 and 3 appear twice.
Example 3
Input: nums = [0,1,2,3,4,5,6,7,8]
Output: 0
Explanation: There is no subsequence of length 5 with a unique middle mode.
Constraints
- 5 <= nums.length <= 1000
- -10^9 <= nums[i] <= 10^9
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