How should I practice Count Equal Reversal-Difference Pairs?

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Count Equal Reversal-Difference Pairs

ZipRecruiter● MediumNEW GRADOA

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Problem statement

Count index pairs (i,j) with i <= j such that numbers[i] + reverse(numbers[j]) == numbers[j] + reverse(numbers[i]). Decimal reversal discards leading zeros.

Function

countReversalPairs(numbers: int[]) → long

Examples

Example 1

numbers = [42,24]return = 2

Both self-pairs and the cross pair qualify because each difference is 18 or -18? The cross equation is equal only for matching differences, so only the two self-pairs qualify.

Example 2

numbers = [10,1]return = 2

The values have different reversal differences, so only their two self-pairs qualify.

Constraints

0 <= numbers.length <= 100000
0 <= numbers[i] <= 1000000000