QuestionA.java

package Q10_05_Sparse_Search;

public class QuestionA {
	public static int search(String[] strings, String str, int first, int last) {
		if (first > last) {
			return -1;
		}
		
		/* Move mid to the middle */
		int mid = (last + first) / 2;
		
		/* If mid is empty, find closest non-empty string. */
		if (strings[mid].isEmpty()) { 
			int left = mid - 1;
			int right = mid + 1;
			while (true) {
				if (left < first && right > last) {
					return -1;
				} else if (right <= last && !strings[right].isEmpty()) {
					mid = right;
					break;
				} else if (left >= first && !strings[left].isEmpty()) {
					mid = left;
					break;
				}
				right++;
				left--;
			}
		}
			
		/* Check for string, and recurse if necessary */
		if (str.equals(strings[mid])) { // Found it!
			return mid;
		} else if (strings[mid].compareTo(str) < 0) { // Search right
			return search(strings, str, mid + 1, last);
		} else { // Search left
			return search(strings, str, first, mid - 1);
		}
	}	
		
	public static int search(String[] strings, String str) {
		if (strings == null || str == null || str.isEmpty()) {
			return -1;
		}
		return search(strings, str, 0, strings.length - 1);
	}
	
	public static void main(String[] args) {
        String[] stringList = {"apple", "", "", "banana", "", "", "", "carrot", "duck", "", "", "eel", "", "flower"};
        System.out.println(search(stringList, "ac"));
        
		//for (String s : stringList) {
		//	String cloned = new String(s);
        //	System.out.println("<" + cloned + "> " + " appears at location " + search(stringList, cloned));
		//}
	}
}