Pairs With a Given Difference

Difficulty: 1300 3000 ms 128 MB

implementation

Count the pairs of positions i < j with |a_i − a_j| = K (K ≥ 0).

Input: the first line has N and K; the second line has N integers.

Output: the number of pairs at absolute difference K.

Constraints:

• 1 ≤ N ≤ 10⁵
• 0 ≤ K ≤ 10⁹
• −10⁹ ≤ a_i ≤ 10⁹

Sample Tests

5 2
1 5 3 4 2

3

4 0
7 7 7 1

3

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