Given an array Arr of N positive integers. Find the number of pairs of integers whose difference is equal to a given number K.
Note: (a, b) and (b, a) are considered same. Also, same numbers at different indices are considered different.
Example 1:
Input:
N = 5
Arr[] = {1, 5, 3, 4, 2}
K = 3
Output: 2
Explanation: There are 2 pairs with difference 3,
the pairs are {1, 4} and {5, 2}
Example 2:
Input:
N = 6
Arr[] = {8, 12, 16, 4, 0, 20}
K = 4
Output: 5
Explanation: There are 5 pairs with difference 4,
the pairs are {0, 4}, {4, 8},
{8, 12}, {12, 16} and {16, 20}
Your Task:
You don't need to read input or print anything. Your task is to complete the function countPairsWithDiffK() which takes the array arr[], n and k as inputs and returns an integer denoting the answer.
Expected Time Complexity: O(N)
Expected Auxiliary Space: O(max(Arr_{i}))
Constraints:
1 <= N <= 10^{5}
0 <= K <= 10^{5}
0 <= Arr_{i} <= 10^{5}

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