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Java program to find non repeating characters in a string

Find non repeating characters in a string

In this article we will learn how to code a java program to find  non-repeating characters in a string. First we will calculate the frequency of each character present in the string as non-repeating characters  are those that are present in the string only once. 

Non repeating characters in a string

Algorithm :

  • Take String as a input from the user.
  • Create array of 256 element to store frequency of each character.
  • Iterate a loop from 0 to length of the string to calculate frequency of each character.
  • Again iterate a loop from 0 to 256 to find the character whose frequency is 1 and also print that character.
  • we will get the desired output.

Solution in Java for finding the non repeating characters in a string

import java.util.*;

class Solution
{
public static void main (String[]args)
{
Scanner sc = new Scanner (System.in);
System.out.println ("Enter the string");

String str = sc.next (); //Taking input as a string from the user
int freq[] = new int[256];

//Calculating frequency of each character
for (int i = 0; i < str.length (); i++)
freq[str.charAt (i)]++;

System.out.println ("The non repeating characters are : ");

for (int i = 0; i < 256; i++)
if (freq[i] == 1) //finding the character whose frequency is 1
System.out.print ((char) i + " ");
}
}

Output :

Enter the string
prepinsta
The non repeating characters are :
a e i n r s t