1331 : D-C Problems

Given n numbers, please count how many pairs of number which satisfy that the difference between the two numbers is equal to c. 

The first line contains a number T representing the number of test cases. 
For each test case: The first line contains two positive integers n, c. The second line contains n integers , all the n integers are not more than $10^{9}$. 
$T \leq 10$
$n \leq 200000, c \leq 10^9$ .

For each test case: Print one integer in a single line, representing the number of pairs satisfy the difference between the two numbers is equal to c. 

1
5 1
1 2 3 4 5

4

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