Find the first non-repeating character in a string.

Question

Anonymous · Accepted Answer

import java.util.*;

class FirstUniq{
    public static void main(String[] args){
        System.out.println(getFirstUniqChar("12"));
    }
    
    public static Character getFirstUniqChar(String s){
        if (s == null || s.length() == 0) {return null;}
        Map map = new LinkedHashMap();
        for(int i = 0; i  e : map.entrySet()){
            if (e.getValue() == 1) return e.getKey();
        }
        return null;
    }
    
}

Scala solution · Answer

def firstNonDup(s: String): Char = {
    val map = s.toCharArray.foldLeft(Map[Char, Int]())((map: Map[Char, Int], c: Char) =>  {
      var m = map
      if (m.contains(c)) {
        m += (c -> m.get(c).get.+(1))
      } else {
        m += (c -> 1)
      }

      m
    })

    val a = s.toCharArray.filter(c => map.get(c).getOrElse(0) == 1)

    a match {
      case Array() => ' '
      case _ => a(0)
    }
  }

C language version · Answer

#include 

char firstNonDup(char *string, int length) {
  int i;
  int cs[256];
  for (i = 0; i < length; i++) {
    cs[string[i]]++;
  }

  for (i = 0; i < length; i++) {
    if (cs[string[i]] == 1) {
        return string[i];
    }
  }

  return ' ';
}

int main(int argc, char **argv) {
  const char string[] = "hello hellen";
  printf("First non-duplicate of %s is %c
", string, firstNonDup(string, sizeof(string)));
}

Anon · Answer

For(i=1 to n)
  If(arr[i] != arr[i-1]) return arr[i-1]

// if we get here the string arr has inly onecharacter repeatef

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