cLcJ49 - Online Python3 Interpreter & Debugging Tool

# your code goes here
# Count All ((i,j) pairs such that b[i] - b[j] == k (count of such pairs.) [i<j]

def func(arr, K):
	freq = {}
	result = 0

	for n in arr:
		result += freq.get(n+K, 0)
		freq[n] = freq.get(n, 0)+1

	return result

def main():
    b = [1, 5, 3, 4, 2]
    k = 2
    print("Count of pairs:", func(b, k))

if __name__ == "__main__":
    main()