Replace every character of string by character whose ASCII value is K times more than it

Last Updated : 08 Feb, 2024

Given string str consisting of lowercase letters only and an integer k, the task is to replace every character of the given string with a character whose ASCII value is k times more than it. If the ASCII value exceeds 'z', then start checking from 'a in a cyclic manner.

Examples:

Input: str = "abc", k = 2
Output: cde
Explanation:
a is moved by 2 times which results in character c
b is moved by 2 times which results in character d
c is moved by 2 times which results in character e

Input: str = "abc", k = 28
Output: cde
Explanation:
a is moved 25 times, z is reached. Then 26th character will be a, 27-th b and 28-th c.
b is moved 24 times, z is reached. 28-th is d.
b is moved 23 times, z is reached. 28-th is e.

Approach: Iterate for every character in the string and perform the below steps for each character:

Add k to the ASCII value of character str[i].
If it exceeds 122, then perform a modulus operation of k with 26 to reduce the number of steps, as 26 is the maximum number of shifts that can be performed in a rotation.
To find the character, add k to 96. Hence, the character with ASCII value k+96 will be a new character.

Repeat the above steps for every character of the given string.

Below is the implementation of the above approach:

C++

// CPP program to move every character
// K times ahead in a given string
#include <bits/stdc++.h>
using namespace std;

// Function to move string character
void encode(string s,int k){

    // changed string
    string newS;

    // iterate for every characters
    for(int i=0; i<s.length(); ++i)
    {
        // ASCII value
        int val = int(s[i]);

        // store the duplicate
        int dup = k;

        // if k-th ahead character exceed 'z'
        if(val + k > 122){
            k -= (122-val);
            k = k % 26;
            newS += char(96 + k);
        }
        else
            newS += char(val + k);

        k = dup;
    }

    // print the new string
    cout<<newS;
}

// driver code
int main(){
    string str = "abc";
    int k = 28;

    // function call
    encode(str, k);

    return 0;
}

// This code is contributed by Sanjit_Prasad

Java

// Java program to move every character 
// K times ahead in a given string 

class GFG {

// Function to move string character 
    static void encode(String s, int k) {

        // changed string 
        String newS = "";

        // iterate for every characters 
        for (int i = 0; i < s.length(); ++i) {
            // ASCII value 
            int val = s.charAt(i);
            // store the duplicate 
            int dup = k;

            // if k-th ahead character exceed 'z' 
            if (val + k > 122) {
                k -= (122 - val);
                k = k % 26;
                
                newS += (char)(96 + k);
            } else {
                newS += (char)(val + k);
            }

            k = dup;
        }

        // print the new string 
        System.out.println(newS);
    }

// Driver Code 
    public static void main(String[] args) {
        String str = "abc";
        int k = 28;

        // function call 
        encode(str, k);
    }
}

// This code is contributed by Rajput-JI

Python3

# Python program to move every character 
# K times ahead in a given string 

# Function to move string character
def encode(s, k):
    
    # changed string 
    newS = ""
    
    # iterate for every characters
    for i in range(len(s)): 
        
        # ASCII value 
        val = ord(s[i]) 
        
        # store the duplicate 
        dup = k 
        
        # if k-th ahead character exceed 'z' 
        if val + k>122: 
            k -= (122-val) 
            k = k % 26
            newS += chr(96 + k) 
            
        else: 
            newS += chr(val + k) 
        
        k = dup 
    
    # print the new string 
    print (newS) 
            
# driver code     
str = "abc"
k = 28

encode(str, k)

// C# program to move every character 
// K times ahead in a given string 
using System;
public class GFG { 

// Function to move string character 
    static void encode(String s, int k) {

        // changed string 
        String newS = "";

        // iterate for every characters 
        for (int i = 0; i < s.Length; ++i) {
            // ASCII value 
            int val = s[i];
            // store the duplicate 
            int dup = k;

            // if k-th ahead character exceed 'z' 
            if (val + k > 122) {
                k -= (122 - val);
                k = k % 26;
                
                newS += (char)(96 + k);
            } else {
                newS += (char)(96 + k);
            }

            k = dup;
        }

        // print the new string 
        Console.Write(newS);
    }

// Driver Code 
    public static void Main() {
        String str = "abc";
        int k = 28;

        // function call 
        encode(str, k);
    }
}

// This code is contributed by Rajput-JI

JavaScript

<script>
// Javascript program to move every character 
// K times ahead in a given string 

    
// Function to move string character 

    function encode(s,k)
    {
        // changed string 
        let newS = "";
  
        // iterate for every characters 
        for (let i = 0; i < s.length; ++i) {
            // ASCII value 
            let val = s[i].charCodeAt(0);
            // store the duplicate 
            let dup = k;
  
            // if k-th ahead character exceed 'z' 
            if (val + k > 122) {
                k -= (122 - val);
                k = k % 26;
                  
                newS += String.fromCharCode(96 + k);
            } else {
                newS += String.fromCharCode(val + k);
            }
  
            k = dup;
        }
  
        // print the new string 
        document.write(newS);
    }
    
    // Driver Code 
    let str = "abc";
    let k = 28;
    
    // function call 
    encode(str, k);
    


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

PHP

<?php
// PHP program to move every character
// K times ahead in a given string

// Function to move string character
function encode($s, $k)
{

    // changed string
    $newS = "";

    // iterate for every characters
    for($i = 0; $i < strlen($s); ++$i)
    {
        // ASCII value
        $val = ord($s[$i]);

        // store the duplicate
        $dup = $k;

        // if k-th ahead character exceed 'z'
        if($val + $k > 122)
        {
            $k -= (122 - $val);
            $k = $k % 26;
            $newS = $newS.chr(96 + $k);
        }
        else
            $newS = $newS.chr($val + $k);

        $k = $dup;
    }

    // print the new string
    echo $newS;
}

// Driver code

$str = "abc";
$k = 28;

// function call
encode($str, $k);

// This code is contributed by ita_c
?>

Output

cde

Complexity Analysis:

Time Complexity: O(N), as we are using a loop to traverse N times so it will cost us O(N) time, where N is the length of the string.
Auxiliary Space: O(N)

Approach: Using modular arithmetic

Steps:

Convert the input string to a list of characters.
Iterate over each character in the list.
Calculate the new ASCII value by adding k to the ASCII value of the current character.
If the new ASCII value exceeds the ASCII value of 'z', wrap around to 'a' by subtracting 26.
Replace the current character in the list with the character corresponding to the new ASCII value.
Convert the list of characters back to a string
Return it as the result.

Below is the implementation of the above approach:

C++

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

// Function to replace characters in a string
string replaceCharacters(string str, int k) {
    // Iterate over each character in the string
    for (int i = 0; i < str.length(); ++i) {
        int asciiVal = (str[i] - 'a' + k) % 26 + 'a'; // Calculate the new ASCII value
        str[i] = static_cast<char>(asciiVal); // Update the character
    }

    return str; // Return the modified string
}
// Driver Code
int main() {
    string inputStr = "abc";
    int kValue = 2;
    string outputStr = replaceCharacters(inputStr, kValue);
    cout << outputStr << endl; 
    return 0;
}

Java

public class GFG {

    public static String replaceCharacters(String str, int k) {
        // Convert the string to a character array
        char[] charArray = str.toCharArray();

        // Iterate over each character in the array
        for (int i = 0; i < charArray.length; ++i) {
            int asciiVal = (charArray[i] - 'a' + k) % 26 + 'a';
            charArray[i] = (char) asciiVal;
        }

        // Convert the character array back to a string
        return new String(charArray);
    }

    public static void main(String[] args) {
        String inputStr = "abc";
        int kValue = 2;
        String outputStr = replaceCharacters(inputStr, kValue);
        System.out.println(outputStr);
    }
}

// This code is contributed by Samim Hossain Mondal.

Python

# Python program to move every character
# K times ahead in a given string


def replace_characters(string, k):
  
    # Convert the string to a list of characters
    char_list = list(string)
    
    # Iterate over each character in the list
    for i in range(len(char_list)):
        ascii_val = (ord(char_list[i]) - ord('a') + k) % 26 + ord('a')
        char_list[i] = chr(ascii_val)
        
    # Convert the list of characters back to a string
    return "".join(char_list)


# Driver Code
input_str = "abc"
k_value = 2
output_str = replace_characters(input_str, k_value)
print(output_str)

using System;

class Program {
    // Function to replace characters in a string
    static string ReplaceCharacters(string str, int k)
    {
        // Create a character array to store the modified
        // characters
        char[] modifiedChars = new char[str.Length];

        // Iterate over each character in the string
        for (int i = 0; i < str.Length; ++i) {
            int asciiVal
                = (str[i] - 'a' + k) % 26
                  + 'a'; // Calculate the new ASCII value
            modifiedChars[i]
                = (char)asciiVal; // Update the character in
                                  // the array
        }

        // Create a new string from the modified character
        // array
        string modifiedStr = new string(modifiedChars);

        return modifiedStr; // Return the modified string
    }

    // Driver Code
    static void Main()
    {
        string inputStr = "abc";
        int kValue = 2;
        string outputStr
            = ReplaceCharacters(inputStr, kValue);
        Console.WriteLine(outputStr);
    }
}

JavaScript

// Function to replace characters in a string
function replaceCharacters(str, k) {
    // Iterate over each character in the string
    for (let i = 0; i < str.length; i++) {
        let charCode = str.charCodeAt(i);
        let newCharCode = ((charCode - 'a'.charCodeAt(0) + k) % 26) + 'a'.charCodeAt(0); // Calculate the new character code
        str = str.substring(0, i) + String.fromCharCode(newCharCode) + str.substring(i + 1); // Update the character
    }

    return str; // Return the modified string
}

// Driver Code
let inputStr = "abc";
let kValue = 2;
let outputStr = replaceCharacters(inputStr, kValue);
console.log(outputStr);

// This code is contributed by shivamgupta0987654321