3395. 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. Since the answer may be very large, return it modulo 109 + 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 contai