Describe and code an algorithm that returns the first duplicate character in a string?

Question

Eric · Accepted Answer

first clarify if it is ASCII or UNICODE string
For ASCII, create BOOL checkArray [128] = {false};
walk the string and update the index of checkArray based of the character. 

for (int index=0;index< strlen(str); index++)
{
if (checkArray[str[index]] == true)
{
  printf (str[index]);
  return;
} 
else
{
    checkArray[str[index]]  = true;
}
}

 · Answer

for (int i=0;i

 · Answer

public static in findDuplicateChar(String s) {
    
        if (s == null)
            return -1;
        
        char[] characters = s.toCharArray();
        
        Map charsMap = HashMap();
        
        for ( int index = 0; index < characters.length; index++ ) {
            // insert the character into the map.  
            // returns null for a new entry
            // returns the index if it previously if it existed
            Integer initialOccurence = charsMap.put(characters[index], index);
            
            if ( initialOccurence != null) {
                return initialOccurance;
            }
            
            //there where no characters that where duplicates
            return -1;
            
        }
    }

Ben · Answer

Simple Python example. Not sure it's most efficient.

def findDup(str):
    match=[]
    i=1
    while (i

 · Answer

Another python solution:

def findFirstNonRepeatedCharInOneIteration(str1):
    for i,j in enumerate(str1):
        if j in str1[:i] or j in str1[i+1:]:
            print "First non-repeated character is "+ j
            break
            
str1 = "abcdefglhjkkjokylf"
findFirstNonRepeatedCharInOneIteration(str1)

 · Answer

function getFirstDuplicateCharacter(str) {
  const seen = new Set();
  for (const char of str) {
    if (seen.has(char)) return char;
    seen.add(char);
  }
}

Rupal Desai · Answer

import java.io.*;
import java.util.*;

/*
 *  code an algorithm that returns the first duplicate character in a string?
 */

class Solution {
  
  public static void main(String[] args) {
    String input = "";
    int j = removeduplicate(input);
    
    if(j == input.length()){
      
    System.out.println("String has unique characters" );
    
    }
    else{
    System.out.println("duplicate character is "+input.charAt(j));
    }
    
    
    
  }
  
  
    public static int removeduplicate(String input){
     
      Set set = new HashSet();
      boolean flag = false;
        int i =0;
        for(; i

 · Answer

import java.io.*;
import java.util.*;
class Solution {
    public static void main(String[] args) {
    String input = "";
    int j = removeduplicate(input);
        if(j == input.length()){
          System.out.println("String has unique characters" );
        }
    else{
    System.out.println("duplicate character is "+input.charAt(j));
    }   
      }
  
  public static int removeduplicate(String input){
           Set set = new HashSet();
      boolean flag = false;
        int i =0;
        for(; i

Rupal · Answer

public static int removeduplicate(String input){
     
      Set set = new HashSet();
      boolean flag = false;
        int i =0;
        for(; i

 · Answer

public class FirstDupCharacter {

	public static void main(String[] args) {
		System.out.println(findDupCharacter("abcdefghiaklmno"));
	}
	
	private static Character findDupCharacter(final String input) {
		final Set set = new HashSet();
		Character dup = null;
		for (int i = 0; i < input.length(); i++) {
			if (set.contains(input.charAt(i))) {
				dup = input.charAt(i);
				break;
			} else {
				set.add(input.charAt(i));
			}
		}
		return dup;
	}
}

Pur · Answer

String samp = "Testing";
		samp = samp.toLowerCase();
		char chararr[] = samp.toCharArray();
		int size = chararr.length;
		char repeat = ' ';
		for (int i=0;i

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Describe and code an algorithm that returns the first duplicate character in a string?

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