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Kotlin program to find first non-repeating character in a string

Here, we are going to learn how to find first non-repeating character in a given string in Kotlin programming language?
Submitted by IncludeHelp, on April 28, 2020

Given a string, we have to find its first non-repeating character.

Example:

    Input:
    string = "includehelp"

    Output:
    First Non-Repeating char in includehelp is i

    Input:
    string = "abcd"

    Output:
    First Non-Repeating char in abcd is a

Program to find first non-repeating character in a string in Kotlin

package com.includehelp.basic

import java.util.*


fun getFirstNonRepeatedChar(str: String): Char? {
	val characterHashMap: HashMap<Char, Int> = HashMap<Char, Int>()
	var c: Char

	// Scan string and build hash table
	for(i in str.indices){
		c = str[i]
		if (characterHashMap.containsKey(c)) {
			// increment count corresponding to c
			characterHashMap[c] = characterHashMap[c]!!+1
		} else {
			characterHashMap[c] = 1
		}
	}

	for(i in str.indices) {
		c = str[i]
		if (characterHashMap.get(c) === 1) return c
	}
	return null
}

//Main Function, entry Point of Program
fun main(args: Array<String>) {
	//Input Stream
	val sc = Scanner(System.`in`)

	//input April20.string value
	println("Input String : ")
	val str: String = sc.nextLine()

	//Get first Non - Repeating Char
	val c= getFirstNonRepeatedChar(str)

	//Print Non Repeating char
	if(c!=null) 
		println("First Non-Repeating char in $str is $c") 
	else 
		System.err.println("NotFound Any Non-Repeating Char")
}

Output

Run 1:
Input String :
includehelp
First Non-Repeating char in includehelp is i
---
Run 2:
Input String :
malayalam
First Non-Repeating char in malayalam is y
---
Run 3:
Input String :
dada
NotFoundAny Non-Repeating Char