How should I practice Count Triplets Within a Value Range?

Start by reading the full statement, solve the visible examples, then compare the pattern against related IBM phone screen problems in FastPrep.

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Count Triplets Within a Value Range

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Problem statement

Given an integer array values and a nonnegative integer d, count index triplets i < j < k for which the difference between the maximum and minimum selected values is at most d.

Return the number of qualifying index triplets. Equal values at different indices are distinct choices.

Function

countBoundedTriplets(values: int[], d: int) → long

Examples

Example 1

values = [1,2,3,4]d = 2return = 2

The qualifying value groups use indices for [1,2,3] and [2,3,4].

Example 2

values = [1,1,1,1]d = 0return = 4

All four choices of three indices have range zero.

Example 3

values = [1,5,9]d = 3return = 0

The only triplet has range 8, which exceeds d.

Constraints

3 <= values.length <= 200000.
-10^9 <= values[i] <= 10^9.
0 <= d <= 2 * 10^9.
The answer fits in a signed 64-bit integer.