summary_ranges.py

'''
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 such that x is in one of the ranges but not in nums.

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

"a->b" if a != b
"a" if a == b
 

Example 1:

Input: nums = [0,1,2,4,5,7]
Output: ["0->2","4->5","7"]
Explanation: The ranges are:
[0,2] --> "0->2"
[4,5] --> "4->5"
[7,7] --> "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] --> "0"
[2,4] --> "2->4"
[6,6] --> "6"
[8,9] --> "8->9"
'''
from typing import List

class Solution:
    def summaryRanges(self, nums:List[int]) -> List[str]:
        ranges = []
        n = len(nums)
        
        if n == 0:
            return ranges
        
        start = nums[0]
        for i in range(1,n):
            # checking if current number is not consecutive
            if nums[i] != nums[i-1] + 1:
                # add current range to the list
                if start == nums[i-1]:
                    ranges.append(f"{start}")
                else:
                    ranges.append(f"{start} -> {nums[i-1]}")
                #updating start of new range
                start = nums[i]
        
        #add the final range
        if start == nums[-1]:
            ranges.append(f"{start}")
        else:
            ranges.append(f"{start} -> {nums[-1]}")
        
        return ranges


nums = [0,1,2,4,5,7]
sol = Solution()
print(sol.summaryRanges(nums))