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Character replacement after removing duplicates from a string

  • Difficulty Level : Basic
  • Last Updated : 22 Apr, 2021

Given a string. The task is to replace each character of the minimized string by a character present at index ‘IND‘ of the original string. The minimized string is the string obtained by removing all duplicates from the original string keeping the order of elements same.

IND for any index in the minimized string is calculated as: 

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IND = (square of ascii value of minimized string character) % (length of original string)



Examples: 

Input : geeks
Output : sesg
Explanation :   minimized string = geks
                length of original string = 5         
                ascii value of g = 103
                IND for g = (103*103) % 5 = 4
                replacement character for g = s 
                character 's' present at index 4 of original string
Similarly,
replacement character for e = e 
replacement character for k = s 
replacement character for s = g 

Input : helloworld
Output : oeoeeoh

Approach:
Below is the step by step algorithm for string minimization:  

    1. Initialize flagchar[26] = {0}
    2. for i=0 to str.length()-1
    3.     ch = str[i]
    4.     if flagchar[ch-97] == 0 then
    5.         mstr = mstr + ch
    6.         flagchar[ch-97] = 1
    7.     End if
    8. End of loop
    9. return mstr  // minimized string

Algorithm for character replacement: 

    1. Replace each character of minimized string as described
       in the problem statement and example
    2. Compute final string 

Below is the implementation of above approach: 

C++




// C++ program for character replacement
// after string minimization
#include <bits/stdc++.h>
using namespace std;
 
// Function to minimize string
string minimize(string str)
{
    string mstr = " ";
    int l, i, flagchar[26] = { 0 };
    char ch;
 
    l = str.length();
 
    // duplicate characters are removed
    for (i = 0; i < str.length(); i++) {
        ch = str.at(i);
 
        // checks if character has previously occurred or not
        // if not then add it to the minimized string 'mstr'
        if (flagchar[ch - 97] == 0) {
            mstr = mstr + ch;
            flagchar[ch - 97] = 1;
        }
    }
 
    return mstr; // minimized string
}
 
// Utility function to print the
// minimized, replaced string
void replaceMinimizeUtil(string str)
{
    string minimizedStr, finalStr = "";
    int i, index, l;
    char ch;
    l = str.length();
 
    minimizedStr = minimize(str); // minimized string
 
    // Creating final string by replacing character
    for (i = 0; i < minimizedStr.length(); i++) {
        ch = minimizedStr.at(i);
 
        // index calculation
        index = (ch * ch) % l;
 
        finalStr = finalStr + str.at(index);
    }
 
    cout << "Final string: " << finalStr; // final string
}
 
// Driver program
int main()
{
    string str = "geeks";
 
    replaceMinimizeUtil(str);
 
    return 0;
}

Java




// Java program for character replacement
// after String minimization
 
class GFG {
    // Function to minimize String
 
    static String minimize(String str)
    {
        String mstr = " ";
        int l, i, flagchar[] = new int[26];
        char ch;
 
        l = str.length();
 
        // duplicate characters are removed
        for (i = 0; i < str.length(); i++) {
            ch = str.charAt(i);
 
            // checks if character has previously occurred or not
            // if not then add it to the minimized String 'mstr'
            if (flagchar[ch - 97] == 0) {
                mstr = mstr + ch;
                flagchar[ch - 97] = 1;
            }
        }
 
        return mstr; // minimized String
    }
 
    // Utility function to print the
    // minimized, replaced String
    static void replaceMinimizeUtil(String str)
    {
        String minimizedStr, finalStr = "";
        int i, index, l;
        char ch;
        l = str.length();
 
        minimizedStr = minimize(str); // minimized String
 
        // Creating final String by replacing character
        for (i = 0; i < minimizedStr.length(); i++) {
            ch = minimizedStr.charAt(i);
 
            // index calculation
            index = (ch * ch) % l;
 
            finalStr = finalStr + str.charAt(index);
        }
        // final String
        System.out.println("Final String: " + finalStr);
    }
 
    // Driver program
    public static void main(String[] args)
    {
        String str = "geeks";
 
        replaceMinimizeUtil(str);
    }
}
// This code is contributed by Rajput-JI

Python3




# Python3 program for character
# replacement after string minimization
 
# Function to minimize string
def minimize(string):
  
    mstr = " "
    flagchar = [0] * 26 
    l = len(string)
     
    # Duplicate characters are removed
    for i in range(0, len(string)):
      
        ch = string[i]
         
        # checks if character has previously occurred or not
        # if not then add it to the minimized string 'mstr'
        if flagchar[ord(ch)-97] == 0:
          
            mstr = mstr + ch
            flagchar[ord(ch)-97] = 1
                  
    return mstr # minimized string
  
# Utility function to print the
# minimized, replaced string
def replaceMinimizeUtil(string):
  
    finalStr = ""
    l = len(string)
    minimizedStr = minimize(string) # minimized string
     
    # Creating final string by replacing character
    for i in range(0, len(minimizedStr)):
      
        ch = ord(minimizedStr[i])
         
        # index calculation
        index = (ch * ch) % l
        finalStr = finalStr + string[index]
     
    print("Final string:", finalStr) # final string
  
# Driver program
if __name__ == "__main__":
  
    string = "geeks"
    replaceMinimizeUtil(string)
 
# This code is contributed by Rituraj Jain

C#




// C# program for character replacement
// after String minimization
using System;
 
class GFG {
 
    // Function to minimize String
    static String minimize(string str)
    {
        string mstr = " ";
        int l, i;
        int[] flagchar = new int[26];
        char ch;
 
        l = str.Length;
 
        // duplicate characters are removed
        for (i = 0; i < str.Length; i++) {
            ch = str[i];
 
            // checks if character has previously
            // occurred or not if not then add it
            // to the minimized String 'mstr'
            if (flagchar[ch - 97] == 0) {
                mstr = mstr + ch;
                flagchar[ch - 97] = 1;
            }
        }
 
        return mstr; // minimized String
    }
 
    // Utility function to print the
    // minimized, replaced String
    static void replaceMinimizeUtil(string str)
    {
        string minimizedStr, finalStr = "";
        int i, index, l;
        char ch;
        l = str.Length;
 
        minimizedStr = minimize(str); // minimized String
 
        // Creating final String by
        // replacing character
        for (i = 0; i < minimizedStr.Length; i++) {
            ch = minimizedStr[i];
 
            // index calculation
            index = (ch * ch) % l;
 
            finalStr = finalStr + str[index];
        }
 
        // final String
        Console.Write("Final String: " + finalStr);
    }
 
    // Driver Code
    public static void Main()
    {
        string str = "geeks";
 
        replaceMinimizeUtil(str);
    }
}
 
// This code is contributed
// by ChitraNayal

PHP




<?php
// PHP program for character replacement
// after string minimization
 
// Function to minimize string
function minimize($str)
{
    $mstr = " ";
    $flagchar=array_fill(0, 26, 0);
 
    $l = strlen($str);
 
    // duplicate characters are removed
    for ($i = 0; $i < strlen($str); $i++)
    {
        $ch = $str[$i];
 
        // checks if character has previously occurred or not
        // if not then add it to the minimized string 'mstr'
        if ($flagchar[ord($ch) - 97] == 0)
        {
            $mstr .=$ch;
            $flagchar[ord($ch) - 97] = 1;
        }
    }
 
    return $mstr; // minimized string
}
 
// Utility function to print the
// minimized, replaced string
function replaceMinimizeUtil($str)
{
 
    $finalStr = "";
 
    $l = strlen($str);
 
    $minimizedStr = minimize($str); // minimized string
 
    // Creating final string by replacing character
    for ($i = 0; $i < strlen($minimizedStr); $i++)
    {
        $ch = $minimizedStr[$i];
 
        // index calculation
        $index = (ord($ch) * ord($ch)) % $l;
 
        $finalStr = $finalStr.$str[$index];
    }
 
    echo "Final string: ".$finalStr; // final string
}
 
// Driver code
$str = "geeks";
 
replaceMinimizeUtil($str);
 
 
// This code is contributed by mits
?>

Javascript




<script>
 
// Javascript program for character replacement
// after String minimization
 
// Function to minimize String
function minimize(str)
{
    let mstr = " ";
    let l, i, flagchar = new Array(26);
     
    for(let i = 0; i < 26; i++)
    {
        flagchar[i] = 0;
    }
    let ch;
 
    l = str.length;
 
    // Duplicate characters are removed
    for(i = 0; i < str.length; i++)
    {
        ch = str[i];
         
        // Checks if character has previously
        // occurred or not if not then add it
        // to the minimized String 'mstr'
        if (flagchar[ch.charCodeAt(0) - 97] == 0)
        {
            mstr = mstr + ch;
            flagchar[ch.charCodeAt(0) - 97] = 1;
        }
    }
     
    // Minimized String
    return mstr;
}
 
// Utility function to print the
// minimized, replaced String
function replaceMinimizeUtil(str)
{
    let minimizedStr, finalStr = "";
    let i, index, l;
    let ch;
    l = str.length;
     
    // Minimized String
    minimizedStr = minimize(str);
 
    // Creating final String by replacing character
    for(i = 0; i < minimizedStr.length; i++)
    {
        ch = minimizedStr[i].charCodeAt(0);
 
        // Index calculation
        index = (ch * ch) % l;
 
        finalStr = finalStr + str[index];
    }
     
    // Final String
    document.write("Final String: " + finalStr);
}
 
// Driver code
let str = "geeks";
 
replaceMinimizeUtil(str);
 
// This code is contributed by avanitrachhadiya2155
 
</script>
Output: 
Final string: ssesg

 

Time Complexity: O(n)

This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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