Question

Jackie is analysing some payment data, stored in
cents, and wants to find pairs of payments that add
up to whole dollar amounts (e.g., 100, 200, 300).
Given a list of payments, calculate the to total
number of payment pairs that can be made.​

Answer 1

Answer:

If |a[j]-a[i]| > 1

f(a[i], a[j]) = a[j] - a[i]

Else // if |a[j]-a[i]| <= 1

f(a[i], a[j]) = 0

Examples:

Input : 6 6 4 4

Output : -8

Explanation:

All pairs are: (6 - 6) + (6 - 6) +

(6 - 6) + (4 - 6) + (4 - 6) + (4 - 6) +

(4 - 6) + (4 - 4) + (4 - 4) = -8

Input: 1 2 3 1 3

Output: 4

Explanation: the pairs that add up are:

(3, 1), (3, 1) to give 4, rest all pairs

according to condition gives 0.

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