Find the first non-repeated character in a string

Question

I read of a job interview question to write some code for the following:

Write an efficient function to find the first nonrepeated character in a st

Answer 1

enter code here

public class FirstRepeatingAndNonRepeatingElements {

/**
 * 
 * @param elements
 * @return
 */
private int firstRepeatedElement(int[] elements) {
    int firstRepeatedElement = -1;
    if(elements!=null && elements.length>0) {
        Set<Integer> setOfElements = new HashSet<>();
        for(int i=elements.length-1;i>=0;i--){
            if(setOfElements.contains(elements[i])) {
                firstRepeatedElement = elements[i];
            } else {
                setOfElements.add(elements[i]);
            }
        }
    }
    return firstRepeatedElement;
}


private int  firstNonRepeatedHashSet(int [] elements)  {
    int firstNonRepatedElement = -1;
    Set<Integer> hashOfElements = new HashSet<>();
    if(elements!=null && elements.length>0) {
        for(int i=elements.length-1;i>=0;i--) {
            if(!hashOfElements.contains(elements[i])) {
                hashOfElements.add(elements[i]);
                firstNonRepatedElement = elements[i];
            }
        }
    }
    return firstNonRepatedElement;
}


/**
 * @param args
 */
public static void main(String[] args) {
    FirstRepeatingAndNonRepeatingElements firstNonRepeatingElement = 
            new FirstRepeatingAndNonRepeatingElements();
    int[] input = new int[]{1,5,3,4,3,5,6,1};

    int firstRepeatedElement = firstNonRepeatingElement.
            firstRepeatedElement(input);

    System.out.println(" The First  Repating Element is "
            + firstRepeatedElement);


    int firstNonRepeatedElement = firstNonRepeatingElement.
            firstNonRepeatedHashSet(input);

    System.out.println(" The First Non Repating Element is "
            + firstNonRepeatedElement);

}

Answer 2

More elegant way

def NotRepeatingCharacter(s):
    for c in s:
        if s.find(c) == s.rfind(c):
            return c
    return '_'

Answer 3

str = "aabcbdefgh"
lst = list(str)

for i in [(item, lst.count(item)) for item in set(lst)]:
    if i[1] == 1:
        print i[0],