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 eInput: 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 charactervoid 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 codeint 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 characterdef 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 = 28encode(str, k) |
C#
// 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 characterfunction 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";$k = 28;// function callencode($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 stringstring 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 Codeint 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 stringdef 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 Codeinput_str = "abc"k_value = 2output_str = replace_characters(input_str, k_value)print(output_str) |
C#
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); }} |
Output
cde
Time Complexity: O(n), where n is the length of the input string.
Auxiliary Space: O(n)
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