LeetCode_FindFirstAndLastPositionElementSortedArray.py

class Solution:
    def searchRange(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        def searchOccurrence(nums, target, isFirst):
            N = len(nums)
            if N == 1: 
                return 0 if target == nums[0] else -1
                
            start, end = 0, N-1
            result = -1
            while start < end:
                mid = start+(end-start)//2
                
                # If target is found, search LEFT, BUT also INCLUDE the mid's value.
                if nums[mid] == target:
                    result = mid
                    if isFirst:
                        end = mid-1
                    else:
                        start = mid+1
                        
                # If target's value is smaller than mid's value, search LEFT
                elif target < nums[mid]:
                    end = mid-1          
                    
                # Else, search RIGHT
                else:
                    start = mid+1                
            # End of while loop.
            return start if (start==end and nums[start]==target) else result    
        # End of helper
        
        first = searchOccurrence(nums, target, isFirst=True)
        last  = searchOccurrence(nums, target, isFirst=False)
        return [first, last]