FirstUniqueCharacterInAString.java

package string;

/**
 * Created by gouthamvidyapradhan on 09/03/2017.
 Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

 Examples:

 s = "leetcode"
 return 0.

 s = "loveleetcode",
 return 2.
 Note: You may assume the string contain only lowercase letters.
 */
public class FirstUniqueCharacterInAString
{
    int[] CHAR = new int[256];
    /**
     * Main method
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception
    {
        System.out.println(new FirstUniqueCharacterInAString().firstUniqChar("loveleetcode"));
    }

    public int firstUniqChar(String s)
    {
        if(s == null || s.isEmpty()) return -1;

        for(int i = 0, l = s.length(); i < l; i ++)
            CHAR[s.charAt(i)]++;

        for(int i = 0, l = s.length(); i < l; i ++)
        {
            if(CHAR[s.charAt(i)] == 1)
                return i;
        }

        return -1;
    }
}