Modify string by replacing characters by alphabets whose distance from that character is equal to its frequency

Given a string S consisting of N lowercase alphabets, the task is to modify the string S by replacing each character with the alphabet whose circular distance from the character is equal to the frequency of the character in S.

Examples:

Input: S = "geeks"
Output: hgglt
Explanation: 
The following modifications are done on the string S:

• The frequency of 'g' in the string is 1. Therefore, 'g' is replaced by 'h'.
• The frequency of 'e' in the string is 2. Therefore, 'e' is replaced by 'g'.
• The frequency of 'e' in the string is 2. Therefore, 'e' is replaced by 'g'.
• The frequency of 'k' in the string is 1. Therefore, 'k' is converted to 'k' + 1 = 'l'.
• The frequency of 's' in the string is 1. Therefore, 's' is converted to 's' + 1 = 't'.

Therefore, the modified string S is "hgglt".

Input: S = "jazz"
Output: "kbbb"

Approach: The given problem can be solved by maintaining the frequency array that stores the occurrences of each character in the string. Follow the steps below to solve the problem:

• Initialize an array, freq[26] initially with all elements as 0 to store the frequency of each character of the string.
• Traverse the given string S and increment the frequency of each character S[i] by 1in the array freq[].
• Traverse the string S used the variable i and performed the following steps:
  • Store the value to be added to S[i] in a variable, add as (freq[i] % 26).
  • If, after adding the value of add to S[i], S[i] does not exceed the character z, then update S[i] to S[i] + add.
  • Otherwise, update the value of add to (S[i] + add - z) and then set S[i] to (a + add - 1).
• After completing the above steps, print the modified string S.

Below is the implementation of the above approach:

// C++ program for the above approach

#include <bits/stdc++.h>
using namespace std;

// Function to modify string by replacing
// characters by the alphabet present at
// distance equal to frequency of the string
void addFrequencyToCharacter(string s)
{
    // Stores frequency of characters
    int frequency[26] = { 0 };

    // Stores length of the string
    int n = s.size();

    // Traverse the given string S
    for (int i = 0; i < n; i++) {

        // Increment frequency of
        // current character by 1
        frequency[s[i] - 'a'] += 1;
    }

    // Traverse the string
    for (int i = 0; i < n; i++) {

        // Store the value to be added
        // to the current character
        int add = frequency[s[i] - 'a'] % 26;

        // Check if after adding the
        // frequency, the character is
        // less than 'z' or not
        if (int(s[i]) + add <= int('z'))
            s[i] = char(int(s[i]) + add);

        // Otherwise, update the value of
        // add so that s[i] doesn't exceed 'z'
        else {
            add = (int(s[i]) + add) - (int('z'));
            s[i] = char(int('a') + add - 1);
        }
    }

    // Print the modified string
    cout << s;
}

// Driver Code
int main()
{
    string str = "geeks";
    addFrequencyToCharacter(str);

    return 0;
}

// Java program for the above approach
class GFG{

// Function to modify string by replacing
// characters by the alphabet present at
// distance equal to frequency of the string
static void addFrequencyToCharacter(char[] s)
{
    
    // Stores frequency of characters
    int frequency[] = new int[26];

    // Stores length of the string
    int n = s.length;

    // Traverse the given string S
    for(int i = 0; i < n; i++) 
    {
        
        // Increment frequency of
        // current character by 1
        frequency[s[i] - 'a'] += 1;
    }

    // Traverse the string
    for(int i = 0; i < n; i++)
    {
        
        // Store the value to be added
        // to the current character
        int add = frequency[s[i] - 'a'] % 26;

        // Check if after adding the
        // frequency, the character is
        // less than 'z' or not
        if ((int)(s[i]) + add <= (int)('z'))
            s[i] = (char)((int)(s[i]) + add);

        // Otherwise, update the value of
        // add so that s[i] doesn't exceed 'z'
        else 
        {
            add = ((int)(s[i]) + add) - ((int)('z'));
            s[i] = (char)((int)('a') + add - 1);
        }
    }

    // Print the modified string
    System.out.println(s);
}

// Driver Code
public static void main(String[] args)
{
    String str = "geeks";
    
    addFrequencyToCharacter(str.toCharArray());
}
}

// This code is contributed by AnkThon

# Python3 program for the above approach

# Function to modify string by replacing
# characters by the alphabet present at
# distance equal to frequency of the string
def addFrequencyToCharacter(s):
    
    # Stores frequency of characters
    frequency = [0] * 26

    # Stores length of the string
    n = len(s)

    # Traverse the given string S
    for i in range(n):
        
        # Increment frequency of
        # current character by 1
        frequency[ord(s[i]) - ord('a')] += 1

    # Traverse the string
    for i in range(n):
        
        # Store the value to be added
        # to the current character
        add = frequency[ord(s[i]) - ord('a')] % 26

        # Check if after adding the
        # frequency, the character is
        # less than 'z' or not
        if (ord(s[i]) + add <= ord('z')):
            s[i] = chr(ord(s[i]) + add)

        # Otherwise, update the value of
        # add so that s[i] doesn't exceed 'z'
        else:
            add = (ord(s[i]) + add) - (ord('z'))
            s[i] = chr(ord('a') + add - 1)

    # Print the modified string
    print("".join(s))

# Driver Code
if __name__ == '__main__':
    
    str = "geeks"
    
    addFrequencyToCharacter([i for i in str])
    
# This code is contributed by mohit kumar 29

// C# program for the above approach
using System;

class GFG{

// Function to modify string by replacing
// characters by the alphabet present at
// distance equal to frequency of the string
static void addFrequencyToCharacter(char[] s)
{
    
    // Stores frequency of characters
    int[] frequency = new int[26];

    // Stores length of the string
    int n = s.Length;

    // Traverse the given string S
    for(int i = 0; i < n; i++)
    {
        
        // Increment frequency of
        // current character by 1
        frequency[s[i] - 'a'] += 1;
    }

    // Traverse the string
    for(int i = 0; i < n; i++) 
    {
        
        // Store the value to be added
        // to the current character
        int add = frequency[s[i] - 'a'] % 26;

        // Check if after adding the
        // frequency, the character is
        // less than 'z' or not
        if ((int)(s[i]) + add <= (int)('z'))
            s[i] = (char)((int)(s[i]) + add);

        // Otherwise, update the value of
        // add so that s[i] doesn't exceed 'z'
        else 
        {
            add = ((int)(s[i]) + add) - ((int)('z'));
            s[i] = (char)((int)('a') + add - 1);
        }
    }

    // Print the modified string
    Console.WriteLine(s);
}

// Driver Code
public static void Main(string[] args)
{
    string str = "geeks";

    addFrequencyToCharacter(str.ToCharArray());
}
}

// This code is contributed by ukasp

<script>
      // JavaScript program for the above approach
      // Function to modify string by replacing
      // characters by the alphabet present at
      // distance equal to frequency of the string
      function addFrequencyToCharacter(s) {
        // Stores frequency of characters
        var frequency = new Array(26).fill(0);

        // Stores length of the string
        var n = s.length;

        // Traverse the given string S
        for (var i = 0; i < n; i++) {
          // Increment frequency of
          // current character by 1
          frequency[s[i].charCodeAt(0) - "a".charCodeAt(0)] += 1;
        }

        // Traverse the string
        for (var i = 0; i < n; i++) {
          // Store the value to be added
          // to the current character
          var add = frequency[s[i].charCodeAt(0) - "a".charCodeAt(0)] % 26;

          // Check if after adding the
          // frequency, the character is
          // less than 'z' or not
          if (s[i].charCodeAt(0) + add <= "z".charCodeAt(0))
            s[i] = String.fromCharCode(s[i].charCodeAt(0) + add);
          // Otherwise, update the value of
          // add so that s[i] doesn't exceed 'z'
          else {
            add = s[i].charCodeAt(0) + add - "z".charCodeAt(0);
            s[i] = String.fromCharCode("a".charCodeAt(0) + add - 1);
          }
        }

        // Print the modified string
        document.write(s.join("") + "<br>");
      }

      // Driver Code
      var str = "geeks";
      addFrequencyToCharacter(str.split(""));
</script>

hgglt

Time Complexity: O(N) //since there is only one loop to carry out the operations the overall time complexity turns out to be O(N)
Auxiliary Space: O(1) //since there is no extra array or data structure used, it takes constant space.