Range-Extraction

About

This is a robust and efficient algorithm that takes a list of integers in increasing order and returns a formatted string in the range-format.

The range-format is a format for expressing an ordered list of integers, it returns a comma separated string of either

• Individual integers
• Or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. The range includes all integers in the interval including both endpoints. It is not considered a range unless it spans at least 3 numbers. For example, "12,13,15-17".

Example:

range_extraction({-10, -9, -8, -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20});
// returns "-10--8,-6,-3-1,3-5,7-11,14,15,17-20"