Codeforces Round 725 (Div. 3) |
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Finished |
You are given an array $$$a$$$ of $$$n$$$ integers. Find the number of pairs $$$(i, j)$$$ ($$$1 \le i < j \le n$$$) where the sum of $$$a_i + a_j$$$ is greater than or equal to $$$l$$$ and less than or equal to $$$r$$$ (that is, $$$l \le a_i + a_j \le r$$$).
For example, if $$$n = 3$$$, $$$a = [5, 1, 2]$$$, $$$l = 4$$$ and $$$r = 7$$$, then two pairs are suitable:
The first line contains an integer $$$t$$$ ($$$1 \le t \le 10^4$$$). Then $$$t$$$ test cases follow.
The first line of each test case contains three integers $$$n, l, r$$$ ($$$1 \le n \le 2 \cdot 10^5$$$, $$$1 \le l \le r \le 10^9$$$) — the length of the array and the limits on the sum in the pair.
The second line contains $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$ ($$$1 \le a_i \le 10^9$$$).
It is guaranteed that the sum of $$$n$$$ overall test cases does not exceed $$$2 \cdot 10^5$$$.
For each test case, output a single integer — the number of index pairs $$$(i, j)$$$ ($$$i < j$$$), such that $$$l \le a_i + a_j \le r$$$.
4 3 4 7 5 1 2 5 5 8 5 1 2 4 3 4 100 1000 1 1 1 1 5 9 13 2 5 5 1 1
2 7 0 1
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