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range_compress.md

Range compression

Write a function compress_ranges that receives an array of integers, and returns a string where consecutive integers are replaced with a range showing the first and last number in that run.

You can assume the array only contains distinct integers, and is always sorted in ascending order.

Test cases

compress_ranges([4,5,6,7])
compress_ranges([1,3,4,5])
compress_ranges([-2,-1,0,1,3,5])
compress_ranges([-5,-4,-3,-1,1])
compress_ranges([-6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20])

Expected output

> compress_ranges([4,5,6,7])
=> "4-7"

> compress_ranges([1,3,4,5])
=> "1,3-5"

> compress_ranges([-2,-1,0,1,3,5])
=> "-2-1,3,5"

> compress_ranges([-5,-4,-3,-1,1])
=> "-5--3,-1,1"

> compress_ranges([-6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20])
=> "-6,-3-1,3-5,7-11,14-15,17-20"
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