careercup1.3: remove duplicate without extra space.

First, ask yourself, what does the interviewer mean by an additional bu#er? Can we use an
additional array of constant size?
Algorithm—No (Large) Additional Memory:
1.  For each character, check if it is a duplicate of already found characters.
2.  Skip duplicate characters and update the non duplicate characters.
Time complexity is O(N2)
Test Cases:
1.  String does not contain any duplicates, e.g.: abcd
2.  String contains all duplicates, e.g.: aaaa
3.  Null string
4.  String with all continuous duplicates, e.g.: aaabbb

 

package careercup;

import java.util.Arrays;

public class test1 {

	public static String checkUnique(char[] s) {
		if(s.length<=1) return new String(s);
		
		int tail = 1;
		for(int i=1; i<s.length; i++){
			int j;
			for(j=0; j<tail; j++){
				if(s[i]==s[j]){
					break;
				}
			}
			if(j==tail){
				s[tail++] = s[i];
			}
		}
		return new String(s, 0, tail);
	}
	
	public static void main(String[] args){
		String s = "abcafasdfgasghfgjkghkfgkffasfasf";
		System.out.println( checkUnique(s.toCharArray()) );
	}
}