34. 在排序数组中查找元素的第一个和最后一个位置 @Python @Go

原题

https://leetcode.cn/problems/find-first-and-last-position-of-element-in-sorted-array/description/

思路

二分查找

复杂度

时间：O(log(n))
空间：O(1)

Python代码

class Solution:
    def searchRange(self, nums: List[int], target: int) -> List[int]:
        if not nums:
            return [-1, -1]
        l, r = 0, len(nums)
        while l < r:
            mid = (l + r) // 2
            if target == nums[mid]:
                left, right = mid, mid
                while left -1 >= 0 and nums[left - 1] == target:
                    left -= 1
                while right + 1 <= len(nums) - 1 and nums[right + 1] == target:
                    right += 1
                return [left, right]
            elif target > nums[mid]:
                l = mid + 1
            else:
                r = mid
        return [-1, -1]  

Go代码

func searchRange(nums []int, target int) []int {
	if len(nums) == 0 {
		return []int{-1, -1}
	}
	l, r := 0, len(nums)
	for l < r {
		mid := (l + r) / 2
		if target == nums[mid] {
			left, right := mid, mid
			for left-1 >= 0 && nums[left-1] == target {
				left--
			}
			for right+1 <= len(nums)-1 && nums[right+1] == target {
				right++
			}
			return []int{left, right}
		} else if target > nums[mid] {
			l = mid + 1
		} else {
			r = mid
		}
	}
	return []int{-1, -1}
}