【leetcode】面试题 10.05. 稀疏数组搜索

题目：

面试题 10.05. 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

二分：

class Solution {
    public int findString(String[] words, String s) {
        int n = words.length;
        int l = 0,r = n - 1;
        while(l <= r) {
            int mid = (l + r) / 2;
            while(l < mid && words[mid].equals("")) mid--;
            if(words[mid].compareTo(s) > 0) r = mid - 1;
            else if(words[mid].compareTo(s) < 0) l = mid + 1;
            else if(words[mid].equals(s)) return mid;
        }
        return -1;
    }
}