Question

I am looking for a solution (preferably JavaScript) that would find gaps in a select set of child ranges compared to their parent range.

Example 1: If I select a parent range of {1,10} and child ranges of {1,2} and {2,10} I would have a gap of 0, meaning the range in the parent range has been completely filled by it’s children.

Example 2: If I select a parent range of {1,10} and child ranges of {1-3} and {6,8} I would have a gap of 4.

Answer 1

1. Sort the child ranges by their initial number
2. Subtract the initial number of the parent range from the initial number of the first child range. This is the start of your running total.
3. Subtract the second number of a range from the initial number of the following range
4. If the result of 3. is positive, add to the running total
5. Finally subtract the second number of the last range from the second number of the parent range, add to running total

The resulting total is the number of missing numbers, assuming you’re only using integers.