二分定位，再前後遍歷

class Solution:
    def searchRange(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        if nums==[]:
            return [-1,-1]
        p = 0
        q = len(nums)
        
        while p < q:
            mid =
 
 (p+q)//2
            if nums[mid] == target:
                break
            elif nums[mid] > target:
                q = mid 
            else:
                p = mid + 1
        if p>=q:
            return [-1,-1]
        l = mid 
        r = mid 
        while l>=0 and nums[l] == target:
 

            l-=1 
        while r<len(nums) and nums[r] == target:
            r+=1
        return [l+1,r-1]