Find one extra character in a string

Given two strings which are of lengths n and n+1. The second string contains all the characters of the first string, but there is one extra character. Your task is to find the extra character in the second string.

Examples:

Input : string strA = "abcd";
        string strB = "cbdae";
Output : e
string B contain all the element 
there is a one extra character which is e

Input : string strA = "kxml";
        string strB = "klxml";
Output : l
string B contain all the element 
there is a one extra character which is l

Method 1(Brute Force):-  Check with two for a loop.

1. Take two input strings s1 and s2 as inputs.
2. Find the length of both strings using the length() function.
3. For each character c in s1, iterate over all characters d in s2 until you find a mismatch. If a mismatch is found, break out of the inner loop and continue with the next character in s1. If all characters in s2 match the character c, then c is the extra character and we can return it.
4. If we reach the end of s1 and have not found an extra character, then the extra character must be the last character in s2.
5. Return the extra character.

C++

#include <iostream>
#include <string>
using namespace std;

char findExtraChar(string s1, string s2)
{
    // input length of strings
    int n1 = s1.length();
    int n2 = s2.length();
    int i, j;
    for (i = 0; i < n1; i++) {
        for (j = 0; j < n2; j++) {
            if (s1[i] == s2[j]) {
                break;
            }
        }
        if (j == n2) {
            return s1[i];
        }
    }
    return s2[n2 - 1];
}

int main()
{
    string s1 = "abcd";
    string s2 = "cbdad";
    cout << findExtraChar(s1, s2) << endl;
    return 0;
}

C#

using System;

class Program {
    static char FindExtraChar(string s1, string s2)
    {
        // get length of strings
        int n1 = s1.Length;
        int n2 = s2.Length;
        int i, j;
        // iterate through the first string
        for (i = 0; i < n1; i++) {
            // iterate through the second string
            for (j = 0; j < n2; j++) {
                // if the current character of the first
                // string matches the current character of
                // the second string, break out of the loop
                // and move on to the next character in the
                // first string
                if (s1[i] == s2[j]) {
                    break;
                }
            }

            // if the loop finished without finding a match,
            // return the current character of the first
            // string
            if (j == n2) {
                return s1[i];
            }
        }

        // if we get to this point, it means that the extra
        // character is at the end of the second string, so
        // return it
        return s2[n2 - 1];
    }

    static void Main(string[] args)
    {
        string s1 = "abcd";
        string s2 = "cbdad";
        Console.WriteLine(FindExtraChar(s1, s2));
    }
}
// This code is contributed by sarojmcy2e

Java

import java.util.*;

public class Main {
    static char findExtraChar(String s1, String s2)
    {
        // input length of strings
        int n1 = s1.length();
        int n2 = s2.length();
        int i, j;
        for (i = 0; i < n1; i++) {
            for (j = 0; j < n2; j++) {
                if (s1.charAt(i) == s2.charAt(j)) {
                    break;
                }
            }
            if (j == n2) {
                return s1.charAt(i);
            }
        }
        return s2.charAt(n2 - 1);
    }
    public static void main(String[] args)
    {
        String s1 = "abcd";
        String s2 = "cbdad";
        System.out.println(findExtraChar(s1, s2));
    }
}
// This code is contributed by sarojmcy2e

Python3

def FindExtraChar(s1, s2):
    # get length of strings
    n1 = len(s1)
    n2 = len(s2)

    # iterate through the first string
    for i in range(n1):
        # iterate through the second string
        for j in range(n2):
            # if the current character of the first
            # string matches the current character of
            # the second string, break out of the loop
            # and move on to the next character in the
            # first string
            if s1[i] == s2[j]:
                break

        # if the loop finished without finding a match,
        # return the current character of the first
        # string
        if j == n2 - 1:
            return s1[i]

    # if we get to this point, it means that the extra
    # character is at the end of the second string, so
    # return it
    return s2[n2 - 1]


s1 = "abcd"
s2 = "cbdad"
print(FindExtraChar(s1, s2))

Javascript

function FindExtraChar(s1, s2) {
    // get length of strings
    let n1 = s1.length;
    let n2 = s2.length;
    let i, j;
    // iterate through the first string
    for (i = 0; i < n1; i++) {
        // iterate through the second string
        for (j = 0; j < n2; j++) {
            // if the current character of the first
            // string matches the current character of
            // the second string, break out of the loop
            // and move on to the next character in the
            // first string
            if (s1[i] == s2[j]) {
                break;
            }
        }

        // if the loop finished without finding a match,
        // return the current character of the first
        // string
        if (j == n2) {
            return s1[i];
        }
    }

    // if we get to this point, it means that the extra
    // character is at the end of the second string, so
    // return it
    return s2[n2 - 1];
}

let s1 = "abcd";
let s2 = "cbdad";
console.log(FindExtraChar(s1, s2));

Output

d

• Time Complexity:- O(n^2) 
• Space Complexity:- O(1)

Method 2: Using Hash Map

Create an empty hash table and insert all character of the second string. Now remove all characters of the first string. The remaining character is the extra character.

Implementation:

C++

// CPP program to find extra character in one
// string
#include <bits/stdc++.h>
using namespace std;

char findExtraCharcter(string strA, string strB)
{
    // store string values in map
    unordered_map<char, int> m1;

    // store second string in map with frequency
    for (int i = 0; i < strB.length(); i++)
        m1[strB[i]]++;

    // store first string in map with frequency
    for (int i = 0; i < strA.length(); i++)
        m1[strA[i]]--;

    for (auto h1 = m1.begin(); h1 != m1.end(); h1++) {

        // if the frequency is 1 then this
        // character is which is added extra
        if (h1->second == 1)
            return h1->first;
    }
}

int main()
{
    // given string
    string strA = "abcd";
    string strB = "cbdad";

    // find Extra Character
    cout << findExtraCharcter(strA, strB);
}

Java

// Java program to find extra character in one
// string
import java.io.*;
class GFG
{

static char findExtraCharcter(char []strA, char[] strB)
{
    // store string values in map
    int[] m1 = new int[256];

    // store second string in map with frequency
    for (int i = 0; i < strB.length; i++)
        m1[strB[i]]++;

    // store first string in map with frequency
    for (int i = 0; i < strA.length; i++)
        m1[strA[i]]--;

    for (int i=0;i<m1.length;i++)
    {

        // if the frequency is 1 then this
        // character is which is added extra
        if (m1[i]== 1)
            return (char) i;
    }
    return Character.MIN_VALUE;
}

// Driver code
public static void main(String[] args)
{
    // given string
    String strA = "abcd";
    String strB = "cbdad";

    // find Extra Character
    System.out.println(findExtraCharcter(strA.toCharArray(), strB.toCharArray()));
    }
}

// This code is contributed by 29AjayKumar

Python3

# Python3 program to find extra character
# in one string
def findExtraCharacter(strA, strB):

    # store string values in map
    m1 = {}

    # store second string in map
    # with frequency
    for i in strB:
        if i in m1:
            m1[i] += 1
        else:
            m1[i] = 1

    # store first string in map
    # with frequency
    for i in strA:
        m1[i] -= 1

    for h1 in m1:

        # if the frequency is 1 then this
        # character is which is added extra
        if m1[h1] == 1:
            return h1

# Driver Code
if __name__ == "__main__":

    # given string
    strA = 'abcd'
    strB = 'cbdad'

    # find Extra Character
    print(findExtraCharacter(strA, strB))

# This code is contributed by
# sanjeev2552

C#

// C# program to find extra character in one
// string
using System;

class GFG
{

static char findExtraCharcter(char []strA, char[] strB)
{
    // store string values in map
    int[] m1 = new int[256];

    // store second string in map with frequency
    for (int i = 0; i < strB.Length; i++)
        m1[strB[i]]++;

    // store first string in map with frequency
    for (int i = 0; i < strA.Length; i++)
        m1[strA[i]]--;

    for (int i = 0; i < m1.Length; i++)
    {

        // if the frequency is 1 then this
        // character is which is added extra
        if (m1[i]== 1)
            return (char) i;
    }
    return char.MinValue;
}

// Driver code
public static void Main(String[] args)
{
    // given string
    String strA = "abcd";
    String strB = "cbdad";

    // find Extra Character
    Console.WriteLine(findExtraCharcter(strA.ToCharArray(),
                                        strB.ToCharArray()));
    }
}

// This code is contributed by Rajput-Ji

Javascript

<script>
// JavaScript program to find extra character in one
// string
function findExtraCharcter(strA,strB)
{

    // store string values in map
    let m1 = new Array(256);
     for(let i = 0; i < 256; i++)
        m1[i] = 0;

    // store second string in map with frequency
    for (let i = 0; i < strB.length; i++)
        m1[strB[i].charCodeAt(0)]++;

    // store first string in map with frequency
    for (let i = 0; i < strA.length; i++)
        m1[strA[i].charCodeAt(0)]--;

    for (let i = 0; i < m1.length; i++)
    {

        // if the frequency is 1 then this
        // character is which is added extra
        if (m1[i] == 1)
            return String.fromCharCode(i);
    }
    return Number.MIN_VALUE;
}

// given string
let strA = "abcd";
let strB = "cbdad";

// find Extra Character
document.write(findExtraCharcter(strA.split(""), strB.split("")));

// This code is contributed by rag2127
</script>

Output:

d

• Time Complexity:- O(n) 
• Auxiliary Space:- O(n). 

Method 3(Bits):- traverse first and second string from starting with the xor operation at the end you get the character which is extra. 

C++

// CPP program to find extra character in one
// string
#include <iostream>
using namespace std;

char findExtraCharcter(string strA, string strB)
{
    // result store the result
    int res = 0, i;

    // traverse string A till end and
    // xor with res
    for (i = 0; i < strA.length(); i++) {

        // xor with res
        res ^= strA[i];
    }

    // traverse string B till end and
    // xor with res
    for (i = 0; i < strB.length(); i++) {

        // xor with res
        res ^= strB[i];
    }

    // print result at the end
    return ((char)(res));
}

int main()
{
    // given string
    string strA = "abcd";
    string strB = "cbdad";
    cout << findExtraCharcter(strA, strB);
    return 0;
}

Java

// Java program to find extra
// character in one string
import java.io.*;

class GFG {

    static char findExtraCharcter(String strA,
                                  String strB)
    {
        // result store the result
        int res = 0, i;

        // traverse string A till
        // end and xor with res
        for (i = 0; i < strA.length(); i++)
        {
            // xor with res
            res ^= strA.charAt(i);
        }

        // traverse string B till end and
        // xor with res
        for (i = 0; i < strB.length(); i++)
        {
            // xor with res
            res ^= strB.charAt(i);
        }

        // print result at the end
        return ((char)(res));
    }

    // Driver code
    public static void main(String args[])
    {
        // given string
        String strA = "abcd";
        String strB = "cbdad";
        System.out.println(findExtraCharcter(strA, strB));
    }
}

/*This code is contributed by Nikita Tiwari.*/

Python 3

# Python 3 program to find
# extra character in one string

def findExtraCharcter(strA, strB) :

    # result store the result
    res = 0

    # traverse string A till
    # end and xor with res
    for i in range(0,len(strA)) :

        # xor with res
        res =res ^ (ord)(strA[i])

    # traverse string B till
    # end and xor with res
    for i in range(0,len(strB)) :

        # xor with res
        res = res ^ (ord)(strB[i])

    # print result at the end
    return ((chr)(res));

# given string
strA = "abcd"
strB = "cbdad"
print(findExtraCharcter(strA, strB))

# This code is contributed by Nikita Tiwari.

C#

// C# program to find extra character
// in one string
using System;

class GFG {

    static char findExtraCharcter(string strA,
                                  string strB)
    {
        // result store the result
        int res = 0, i;

        // traverse string A till end and
        // xor with res
        for (i = 0; i < strA.Length; i++) {

            // xor with res
            res ^= strA[i];
        }

        // traverse string B till end and
        // xor with res
        for (i = 0; i < strB.Length; i++) {

            // xor with res
            res ^= strB[i];
        }

        // print result at the end
        return ((char)(res));
    }

    // Driver Code
    public static void Main()
    {
        // given string
        string strA = "abcd";
        string strB = "cbdad";
        Console.WriteLine(
            findExtraCharcter(strA, strB));
    }
}

// This code is contributed by Manish Shaw
// (manishshaw1)

PHP

<?php
// PHP program to find extra character in
// one string

function findExtraCharcter($strA, $strB)
{
    // result store the result
    $res = 0;

    // traverse string A till end and
    // xor with res
    for ($i = 0; $i < strlen($strA); $i++)
    {

        // xor with res
        $res ^= ord($strA[$i]);
    }

    // traverse string B till end and
    // xor with res
    for ($i = 0; $i < strlen($strB); $i++)
    {

        // xor with res
        $res ^= ord($strB[$i]);
    }

    // print result at the end
    return $res;
}

// Driver code
$strA = "abcd";
$strB = "cbdad";
echo chr(findExtraCharcter($strA, $strB));

// This code is contributed by Manish Shaw
// (manishshaw1)
?>

Javascript

<script>
// Javascript program to find extra character in
// one string

function findExtraCharcter(strA, strB)
{
    // result store the result
    let res = 0;

    // traverse string A till end and
    // xor with res
    for (let i = 0; i < strA.length; i++)
    {

        // xor with res
        res ^= strA.charCodeAt(i);
    }

    // traverse string B till end and
    // xor with res
    for (let i = 0; i < strB.length; i++)
    {

        // xor with res
        res ^= strB.charCodeAt(i);
    }

    // print result at the end
    return res;
}

// Driver code
let strA = "abcd";
let strB = "cbdad";
document.write(String.fromCharCode(findExtraCharcter(strA, strB)));



// This code is contributed by gfgking
</script>

Output:

d

• Time Complexity:- O(n+n+1) 
• Space Complexity:- O(1).

Method 4(Character Code):

Add the character codes of both strings. Minus character codes of smaller strings from larger string and convert the resulting integer into a character.

Implementation:

C++

    // C++ program to find extra
// character in one string
#include<bits/stdc++.h>
using namespace std;

char findExtraCharacter(string s1, string s2)
{
    string smallStr;
    string largeStr;

    // Determine string with extra character.
    if(s1.size() > s2.size())
    {
        smallStr = s2;
        largeStr = s1;
    }
    else
    {
        smallStr = s1;
        largeStr = s2;
    }

    int smallStrCodeTotal = 0;
    int largeStrCodeTotal = 0;
    int i = 0;

    // Add character codes of both the strings
    for(; i < smallStr.size(); i++)
    {
        smallStrCodeTotal += smallStr[i];
        largeStrCodeTotal += largeStr[i];
    }

    // Add last character code of large string.
    largeStrCodeTotal += largeStr[i];

    // Minus the character code of smaller string from
    // the character code of large string.
    // The result will be the extra character code.
    int intChar = largeStrCodeTotal - smallStrCodeTotal;
    return (char)intChar;
}

// Driver code
int main()
{
    string s1 = "abcd";
    string s2 = "cbdae";

    char extraChar = findExtraCharacter(s1, s2);
    cout<<"Extra character: " <<(extraChar)<<endl;
    return 0;
}

// This code is contributed by Princi Singh

Java

// Java program to find extra
// character in one string
import java.io.*;
public class Test {

    private static char findExtraCharacter(String s1, String s2) {
        String smallStr;
        String largeStr;

        // Determine String with extra character.
        if(s1.length() > s2.length()) {
            smallStr = s2;
            largeStr = s1;
        } else {
            smallStr = s1;
            largeStr = s2;
        }

        int smallStrCodeTotal = 0;
        int largeStrCodeTotal = 0;
        int i = 0;

        // Add character codes of both the strings
        for(; i < smallStr.length(); i++) {
            smallStrCodeTotal += smallStr.charAt(i);
            largeStrCodeTotal += largeStr.charAt(i);
        }

        // Add last character code of large String.
        largeStrCodeTotal += largeStr.charAt(i);

        // Minus the character code of smaller string from
        // the character code of large string.
        // The result will be the extra character code.
        int intChar = largeStrCodeTotal - smallStrCodeTotal;
        return (char)intChar;
    }

    public static void main(String[] args) {
        String s1 = "abcd";
        String s2 = "cbdae";

        char extraChar = findExtraCharacter(s1, s2);
        System.out.println("Extra character: " + extraChar);

    }
}


/*This code is contributed by Amol Bhosale.*/

Python3

# Python Program to find extra character in one string
def findExtraCharacter(s1,s2):
    smallStr = ""
    largeStr = ""

    # Determine string with extra character
    if(len(s1) > len(s2)):
        smallStr = s2
        largeStr = s1
    else:
        smallStr = s1
        largeStr = s2
    smallStrCodeTotal = 0
    largeStrCodeTotal = 0
    i = 0

    # Add Character codes of both the strings
    while(i < len(smallStr)):
        smallStrCodeTotal += ord(smallStr[i])
        largeStrCodeTotal += ord(largeStr[i])
        i += 1

    # Add last character code of large string
    largeStrCodeTotal += ord(largeStr[i])

    # Minus the character code of smaller string
    # from the character code of large string
    # The result will be the extra character code
    intChar = largeStrCodeTotal - smallStrCodeTotal
    return chr(intChar)

# Driver code
s1 = "abcd"
s2 = "cbdae"
extraChar = findExtraCharacter(s1, s2)
print("Extra Character:", extraChar)

# This code is contributed by simranjenny84

C#

// C# program to find extra
// character in one string
using System;

class GFG
{
    private static char findExtraCharacter(String s1,
                                           String s2)
    {
        String smallStr;
        String largeStr;

        // Determine String with extra character.
        if(s1.Length > s2.Length)
        {
            smallStr = s2;
            largeStr = s1;
        }
        else
        {
            smallStr = s1;
            largeStr = s2;
        }

        int smallStrCodeTotal = 0;
        int largeStrCodeTotal = 0;
        int i = 0;

        // Add character codes of both the strings
        for(; i < smallStr.Length; i++)
        {
            smallStrCodeTotal += smallStr[i];
            largeStrCodeTotal += largeStr[i];
        }

        // Add last character code of large String.
        largeStrCodeTotal += largeStr[i];

        // Minus the character code of smaller string
        // from the character code of large string.
        // The result will be the extra character code.
        int intChar = largeStrCodeTotal -
                      smallStrCodeTotal;
        return (char)intChar;
    }

    public static void Main(String[] args)
    {
        String s1 = "abcd";
        String s2 = "cbdae";

        char extraChar = findExtraCharacter(s1, s2);
        Console.WriteLine("Extra character: " +
                                    extraChar);
    }
}

// This code is contributed by PrinciRaj1992

Javascript

<script>
// Javascript program to find extra
// character in one string
function findExtraCharacter(s1, s2)
{
        let smallStr;
        let largeStr;

        // Determine String with extra character.
        if(s1.length > s2.length)
        {
            smallStr = s2;
            largeStr = s1;
        }
        else
        {
            smallStr = s1;
            largeStr = s2;
        }

        let smallStrCodeTotal = 0;
        let largeStrCodeTotal = 0;
        let i = 0;

        // Add character codes of both the strings
        for(; i < smallStr.length; i++)
        {
            smallStrCodeTotal += smallStr[i].charCodeAt(0);
            largeStrCodeTotal += largeStr[i].charCodeAt(0);
        }

        // Add last character code of large String.
        largeStrCodeTotal += largeStr[i].charCodeAt(0);

        // Minus the character code of smaller string from
        // the character code of large string.
        // The result will be the extra character code.
        let intChar = largeStrCodeTotal - smallStrCodeTotal;

        return String.fromCharCode(intChar);
}

let s1 = "abcd";
let s2 = "cbdae";

let extraChar = findExtraCharacter(s1, s2);
document.write("Extra character: " + extraChar);

// This code is contributed by avanitrachhadiya2155
</script>

Output:

Extra character: e

• Time Complexity:- O(n) 
• Auxiliary Space:- O(1)