Count the Number of Fair Pairs
Medium
You receive a 0-indexed integer array nums of size n and two integers lower and upper, provide the count of fair pairs.
A pair (i, j) is fair if:
-
0 <= i < j < n, and -
lower <= nums[i] + nums[j] <= upper
Example 1
Input: nums = [0,1,7,4,4,5], lower = 3, upper = 6
Output: 6
Explanation: There are 6 fair pairs: (0,3), (0,4), (0,5), (1,3), (1,4), and (1,5).
Example 2
Input: nums = [1,7,9,2,5], lower = 11, upper = 11
Output: 1
Explanation: There is a single fair pair: (2,3).
Constraints
1 <= nums.length <= 10^5nums.length == n-10^9<= nums[i] <= 10^9-10^9<= lower <= upper <= 10^9
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