面试题 10.05. 稀疏数组搜索(折中查找 + 递归 实现)

/**
 *	面试题 10.05. 稀疏数组搜索
 *	@author wsq
 *	@date 2020/10/09
	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
	
	链接：https://leetcode-cn.com/problems/sparse-array-search-lcci
 */
package search;

public class FindString {
	int ans = -1;
	/**
	 *	折中查找 + 递归实现
	 * @param words
	 * @param s
	 * @return
	 */
    public int findString(String[] words, String s) {
        int n = words.length;
        int left = 0;
        int right = n - 1;
        findString(words, s, left, right);
        return ans;
    }
    
    public void findString(String[] words, String target, int left, int right){
        if(ans != -1){
            return;
        }
        if(left > right) {
        	return;
        }
        int mid = (left + right) >> 1;
        
        if(words[mid] == target){
            ans = mid;
            return;
        }
        if("".equals(words[mid])){
            findString(words, target, left, mid - 1);
            findString(words, target, mid + 1, right);
        }else if(words[mid].compareTo(target) > 0){
            findString(words, target, left, mid - 1);
        }else{
            findString(words, target, mid + 1, right);
        }
    }
    public static void main(String[] args) {
    	String[] words = {"at", "", "", "", "ball", "", "", "car", "", "", "dad", "", ""};
    	String s = "ball";
    	FindString fs = new FindString();
    	int ans = fs.findString(words, s);
    	System.out.println(ans);
	}
}