Find First and Last Position of Element in Sorted Array
Created: October 26, 2018 by [lek-tin]
Last updated: September 22, 2019
Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.
Your algorithm’s runtime complexity must be in the order of O(log n).
If the target is not found in the array, return [-1, -1].
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]
Solution
Time: O(logN)
class Solution:
def searchRange(self, nums: List[int], target: int) -> List[int]:
res = [-1, -1]
n = len(nums)
if not nums or n == 0:
return res
start, end = 0, n-1
while start+1 < end:
mid = start + (end-start)//2
if nums[mid] >= target:
end = mid
else:
start = mid
if nums[start] == target:
res[0] = start
elif nums[end] == target:
res[0] = end
start, end = 0, n-1
while start+1 < end:
mid = start + (end-start)//2
if nums[mid] <= target:
start = mid
else:
end = mid
if nums[end] == target:
res[1] = end
elif nums[start] == target:
res[1] = start
return res