37-SearchRangeLimits.py

'''
Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value.

If target is not found in the array, return [-1, -1].

You must write an algorithm with O(log n) runtime complexity.

 

Example 1:

Input: nums = [5,7,7,8,8,10], target = 8
Output: [3,4]
Example 2:

Input: nums = [5,7,7,8,8,10], target = 6
Output: [-1,-1]
Example 3:

Input: nums = [], target = 0
Output: [-1,-1]
 

Constraints:

0 <= nums.length <= 105
-109 <= nums[i] <= 109
nums is a non-decreasing array.
-109 <= target <= 109
'''


class Solution:
    def searchRange(self, nums: List[int], target: int) -> List[int]:
        def bs(isLeftSearch):
            lo = 0
            hi = len(nums) - 1
            ind = -1
            
            while lo <= hi:
                mid = (lo + hi)//2
                if nums[mid] == target:
                    ind = mid
                    if isLeftSearch:        # Important, otherwise doesn't work for half of the cases
                        hi = mid - 1
                    else:
                        lo = mid + 1
                elif nums[mid] <= target:
                    lo = mid + 1
                else:
                    hi = mid - 1
            return ind
        
        start = bs(True)
        end = bs(False)
        return [start, end]