Count Pairs Whose Sum is Less than Target

Statement

You are given a 0-indexed integer array, nums, of length $n$, and an integer target. Your task is to determine the number of distinct pairs of indices $(i, j)$ such that:

• $0 \leq i < j < n$ (i.e., $i$ comes before $j$ in the array)

• The sum of the elements of the indices $(i, j)$, (i.e., $nums[i]+nums[j]$), is strictly less than target.

Constraints:

• $1 \leq$ nums.length $==$ $n\leq 50$

• $-50 \leq$ nums[i], target $\leq 50$

Examples