题目

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:

1. words的长度在[1, 1000000]之间

题解

public int findString(String[] words, String s) {
    BiFunction<Integer, Integer, Integer> binarySearch = new BiFunction<Integer, Integer, Integer>() {
        @Override
        public Integer apply(Integer left, Integer right) {
            // 左右区间压缩
            while (left <= right && words[left].isEmpty()) {
                left++;
            }
            while (right >= 0 && words[right].isEmpty()) {
                right--;
            }

            // 未找到结果
            if (left > right) {
                return -1;
            }

            // 中位压缩
            int mid = (left + right) >> 1;
            while (words[mid].isEmpty()) {
                mid--;
            }

            int compare = words[mid].compareTo(s);
            return compare == 0 ? mid : (compare > 0 ? this.apply(left, mid - 1) : this.apply(mid + 1, right));
        }
    };

    return binarySearch.apply(0, words.length - 1);
}