python 稀疏数组搜索

| 稀疏数组搜索

稀疏数组搜索。有个排好序的字符串数组，其中散布着一些空字符串，编写一种方法，找出给定字符串的位置。

示例1:

 输入: words = ["at", "", "", "", "ball", "", "", "car", "", "","dad", "", ""], s = "ta"
 输出：-1
 说明: 不存在返回-1。
示例2:

 输入：words = ["at", "", "", "", "ball", "", "", "car", "", "","dad", "", ""], s = "ball"
 输出：4
提示:

words的长度在[1, 1000000]之间

题解

class Solution:
    def findString(self, words: List[str], s: str) -> int:
        length = len(words)
        first = 0
        last = length - 1

        while last >= first:
            mid = first + (last-first)//2
            if words[mid] == s:
                return mid
            elif words[mid] > s:
                last = mid - 1
            else:
                first = first + 1
       
        return -1