Program to Find the Duplicate Characters in a String

Program to find the duplicate characters in a string

Explanation

In this program, we need to find the duplicate characters in the string.

To find the duplicate character from the string, we count the occurrence of each character in the string. If count is greater than 1, it implies that a character has a duplicate entry in the string. In above example, the characters highlighted in green are duplicate characters.

Algorithm

Define a string.
Two loops will be used to find the duplicate characters. Outer loop will be used to select a character and initialize variable count by 1.
Inner loop will compare the selected character with rest of the characters present in the string.
If a match found, it increases the count by 1 and set the duplicates of selected character by '0' to mark them as visited.
After inner loop, if count of character is greater than 1, then it has duplicates in the string.

Solution

Python

string = "Great responsibility";
 
print("Duplicate characters in a given string: ");
#Counts each character present in the string
for i in range(0, len(string)):
    count = 1;
    for j in range(i+1, len(string)):
        if(string[i] == string[j] and string[i] != ' '):
            count = count + 1;
            #Set string[j] to 0 to avoid printing visited character
            string = string[:j] + '0' + string[j+1:];
 
    #A character is considered as duplicate if count is greater than 1
    if(count > 1 and string[i] != '0'):
        print(string[i]);

Output:

 Duplicate characters in a given string: 
r
e
t
s
i

C

#include <stdio.h>
#include <string.h>
 
int main()
{
    char string[] = "Great responsibility";
    int count;
    
    printf("Duplicate characters in a given string: \n");
    //Counts each character present in the string
    for(int i = 0; i < strlen(string); i++) {
        count = 1;
        for(int j = i+1; j < strlen(string); j++) {
            if(string[i] == string[j] && string[i] != ' ') {
                count++;
                //Set string[j] to 0 to avoid printing visited character
                string[j] = '0';
            }
        }
        //A character is considered as duplicate if count is greater than 1
        if(count > 1 && string[i] != '0')
            printf("%c\n", string[i]);
    }
 
    return 0;
}

Output:

Duplicate characters in a given string: 
r
e
t
s
i

JAVA

public class DuplicateCharacters {
     public static void main(String[] args) {
        String string1 = "Great responsibility";
        int count;
        
        //Converts given string into character array
        char string[] = string1.toCharArray();
        
        System.out.println("Duplicate characters in a given string: ");
        //Counts each character present in the string
        for(int i = 0; i <string.length; i++) {
            count = 1;
            for(int j = i+1; j <string.length; j++) {
                if(string[i] == string[j] && string[i] != ' ') {
                    count++;
                    //Set string[j] to 0 to avoid printing visited character
                    string[j] = '0';
                }
            }
            //A character is considered as duplicate if count is greater than 1
            if(count > 1 && string[i] != '0')
                System.out.println(string[i]);
        }
    }
}

Output:

Duplicate characters in a given string: 
r
e
t
s
i

C#

using System;
                    
public class DuplicateCharacters
{
    public static void Main()
    {
        String str = "Great responsibility";
        int count;
        
        //Converts given string into character array
        char[] string1 = str.ToCharArray();
        
        Console.WriteLine("Duplicate characters in a given string: ");
        //Counts each character present in the string
        for(int i = 0; i <string1.Length; i++) {
            count = 1;
            for(int j = i+1; j <string1.Length; j++) {
                if(string1[i] == string1[j] && string1[i] != ' ') {
                    count++;
                    //Set string1[j] to 0 to avoid printing visited character
                    string1[j] = '0';
                }
            }
            //A character is considered as duplicate if count is greater than 1
            if(count > 1 && string1[i] != '0')
                Console.WriteLine(string1[i]);
        }
    }
}

Output:

Duplicate characters in a given string: 
r
e
t
s
i

PHP

<!DOCTYPE html>
<html>
<body>
<?php
$string = "Great responsibility";
$count;
 
print("Duplicate characters in a given string: <br>");
//Counts each character present in the string
for($i = 0; $i < strlen($string); $i++) {
    $count = 1;
    for($j = $i+1; $j < strlen($string); $j++) {
        if($string[$i] == $string[$j] && $string[$i] != ' ') {
            $count++;
            //Set $string[$j] to 0 to avoid printing visited character
            $string[$j] = '0';
        }
    }
    //A character is considered as duplicate if count is greater than 1
    if($count > 1 && $string[$i] != '0'){
        print($string[$i]);
        print("<br>");
    }
}
?>
</body>
</html>

Output:

Duplicate characters in a given string: 
r
e
t
s
i

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