Summary Ranges

Summary Ranges

You are given a sorted unique integer array nums.

A range [a, b] is the set of all integers from a to b (inclusive).

Return the smallest sorted list of ranges that cover all the numbers in the array exactly. That is, each element of nums is covered by exactly one of the ranges, and there is no integer x in a range that is not in nums.

Each range [a, b] in the output should be formatted as:

• "a->b" if a != b
• "a" if a == b

Examples

Example 1:

Input: nums = [0, 1, 2, 4, 5, 7]
Output: ["0->2", "4->5", "7"]
Explanation: The ranges are [0,2], [4,5], and [7].

Example 2:

Input: nums = [0, 2, 3, 4, 6, 8, 9]
Output: ["0", "2->4", "6", "8->9"]
Explanation: The ranges are [0,0], [2,4], [6,6], and [8,9].

Example 3:

Input: nums = []
Output: []

Constraints

• 0 <= nums.length <= 20
• -2^31 <= nums[i] <= 2^31 - 1
• All values in nums are unique
• nums is sorted in ascending order

Expected Complexity

• Time: O(n)
• Space: O(1). excluding the output array