Compress Consecutive Runs

Easy

A warehouse logs the box numbers it ships and wants them written compactly. You are given a strictly increasing list of distinct integers ids. Split it into maximal runs of consecutive numbers with no gaps (each next number is exactly 1 more than the previous one). Write each run as a string: - "a->b" if the run starts at a and ends at b, with a != b; - "a" if the run is a single number. Return the strings in increasing order. Every number in ids must belong to exactly one run, and no run may contain a number that is not in ids.

Example 1

ids=[3, 4, 5, 6, 10, 12, 13] → ['3->6', '10', '12->13']

Numbers 3 to 6 are consecutive and collapse into "3->6", 10 stands alone, and 12, 13 give "12->13".

Example 2

ids=[-2, 0, 1] → ['-2', '0->1']

-1 is missing between -2 and 0, so -2 is a range of its own.

Example 3

ids=[] → []

No numbers, no ranges.

Constraints

0 ≤ len(ids) ≤ 20
-2³¹ ≤ ids[i] ≤ 2³¹ - 1
The values in ids are distinct and sorted in increasing order

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Topics

Array

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Input

ids=[3, 4, 5, 6, 10, 12, 13]

Expected

['3->6', '10', '12->13']

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