Find The First Non Repeated Character In A String

First we need to understand the question , we need to write an algorithm for  the first non repeated character in a string , for example :

Read Also :   Count number of words in the String

If the word "stress" is input  then it should print  't'   as output .

If the word "teeter" is input  then it should print  'r'   as output .

Now , we should understand the pseudo algorithm or logic to achieve this task , code is given in the end of this post .


As we know a non repeated character occurs only once in the string , so if we store the number of times
each alphabet appears in the string , it would help us identifying which characters are non repeated characters in the string .So we need to scan the whole string and determine the final counts of each character . Now scan the final values of each character in the string , the first character in the string with final count 1 is the first non repeated character in the string.

Pseudo Algorithm

1.   First create the  character count hash table .
          For each character
            If there is no value stored in the character
                     set it to 1 .
                     increment the value of the character by 1 .

2.  Scan the string
           For each character
           return character if the count in hash table is 1 .
           If no character have count 1 , return null

asked Aug 28, 2015 in Core java by rajesh
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