Skip to content

Minimum cost to convert string into palindrome

Minimum reduce operations to convert a given string into a palindrome

Last Updated : 02 Jan, 2023

Given a String find the minimum number of reduce operations required to convert a given string into a palindrome. In a reduce operation, we can change character to a immediate lower value. For example b can be converted to a.

Examples :

Input  :  abcd   Output :  4 We need to reduce c once and d three times.  Input  : ccc Output : 0

The idea is simple. We traverse string from left and compare characters of left half with their corresponding characters in right half. We add difference between to characters to result.

Implementation:

C++

   // CPP program to count minimum reduce
// operations to make a palindrome
#include <bits/stdc++.h>
using namespace std;
 
// Returns count of minimum character
// reduce operations to make palindrome.
int countReduce(string& str)
{
    int n = str.length();
    int res = 0;
 
    // Compare every character of first half
    // with the corresponding character of
    // second half and add difference to
    // result.
    for (int i = 0; i < n / 2; i++)
        res += abs(str[i] - str[n - i - 1]);
 
    return res;
}
 
// Driver code
int main()
{
    string str = "abcd";
    cout << countReduce(str);
    return 0;
}
 
  

Java

   // Java program to count minimum reduce
// operations to make a palindrome
import java.io.*;
 
class GFG 
{
    // Returns count of minimum character
    // reduce operations to make palindrome.
    static int countReduce(String str)
    {
        int n = str.length();
        int res = 0;
     
        // Compare every character of first half
        // with the corresponding character of
        // second half and add difference to
        // result.
        for (int i = 0; i < n / 2; i++)
            res += Math.abs(str.charAt(i) 
                   - str.charAt(n - i - 1));
     
        return res;
    }
     
    // Driver code
    public static void main (String[] args) 
    {
        String str = "abcd";
        System.out.println( countReduce(str));
             
    }
}
 
// This code is contributed by vt_m.
 
  

Python3

   # python3 program to count minimum reduce
# operations to make a palindrome
 
# Returns count of minimum character
# reduce operations to make palindrome.
def countReduce(str):
 
    n = len(str)
    res = 0
 
    # Compare every character of first half
    # with the corresponding character of
    # second half and add difference to
    # result.
    for i in range(0, int(n/2)):
        res += abs( int(ord(str[i])) -
               int(ord(str[n - i - 1])) )
     
    return res
 
# Driver code
str = "abcd"
print(countReduce(str))
 
# This code is contributed by Sam007
 
  

C#

   // C# program to count minimum reduce
// operations to make a palindrome
using System;
 
class GFG {
     
    // Returns count of minimum character
    // reduce operations to make palindrome.
    static int countReduce(string str)
    {
        int n = str.Length;
        int res = 0;
     
        // Compare every character of first
        // half with the corresponding 
        // character of second half and 
        // add difference to result.
        for (int i = 0; i < n / 2; i++)
            res += Math.Abs(str[i] 
                    - str[n - i - 1]);
     
        return res;
    }
     
    // Driver code
    public static void Main () 
    {
        string str = "abcd";
        Console.WriteLine( countReduce(str));
             
    }
}
 
// This code is contributed by vt_m.
 
  

PHP

   <?php
// PHP program to count minimum
// reduce operations to make a 
// palindrome
 
// Returns count of minimum 
// character reduce operations 
// to make palindrome.
function countReduce($str)
{
    $n = strlen($str);
    $res = 0;
 
    // Compare every character 
    // of first half with the 
    // corresponding character 
    // of second half and add 
    // difference to result.
    for ($i = 0; $i < $n / 2; $i++)
        $res += abs(ord($str[$i]) - 
                    ord($str[($n - $i - 1)]));
    return $res;
}
 
// Driver code
$str = "abcd";
echo countReduce($str);
 
// This code is contributed by Sam007
?>
 
  

Javascript

   <script>
    // Javascript program to count minimum reduce
    // operations to make a palindrome
     
    // Returns count of minimum character
    // reduce operations to make palindrome.
    function countReduce(str)
    {
        let n = str.length;
        let res = 0;
       
        // Compare every character of first
        // half with the corresponding 
        // character of second half and 
        // add difference to result.
        for (let i = 0; i < parseInt(n / 2, 10); i++)
            res += Math.abs(str[i].charCodeAt() - str[n - i - 1].charCodeAt());
       
        return res;
    }
        
      let str = "abcd";
      document.write(countReduce(str));
     
</script>
 
  

Output

Time Complexity: O(n) where n is the length of the string
Auxiliary Space: O(1)

Minimum cost to convert string into palindrome

GeeksforGeeks

Improve

Article Tags :

Practice Tags :

Similar Reads

Minimum cost to convert the given String into Palindrome

Given a string S of length N and 2 integers X and Y, the task is to find the minimum cost of converting the string to a palindrome by performing the following operations any number of times in any order: Move the leftmost character to the rightmost end of the string at cost X. i.e S1S2...SN gets con

Minimum cost to convert string into palindrome

Convert string S into a palindrome string. You can only replace a character with any other character. When you replace character 'a' with any other character, it costs 1 unit, similarly for 'b' it is 2 units ..... and for 'z', it is 26 units. Find the minimum cost required to convert string S into p

Minimize cost to convert given string to a palindrome

Given a string S of length N and an integer P denoting a pointer to Pth index of the string, the task is to find the minimum cost to convert the string into a palindrome by performing the following operations: Pointer P can be moved from index i to index j and the cost required is |i - j| where 0 ?

Minimum number of characters to be replaced to make a given string Palindrome

Given string str, the task is to find the minimum number of characters to be replaced to make a given string palindrome. Replacing a character means replacing it with any single character in the same position. We are not allowed to remove or add any characters. If there are multiple answers, print t

Minimum cuts required to convert a palindromic string to a different palindromic string

Given palindromic string s, the task is to find minimum k, such that you can cut this string into k+1 parts, and then unite them in such a way that the final string will be a palindrome and it won't be equal to the initial string s. If it is impossible then print -1.Examples: Input : string = "civic

Minimize operations to make String palindrome by incrementing prefix by 1

Given a string S of numbers of length N, the task is to find the minimum number of operations required to change a string into palindrome and we can perform the following procedure on the string : Choose an index i (0 ? i < N) and for all 0 ? j ? i, set Sj = Sj + 1 (i.e. add 1 to every element in

Minimizing Operations to Prevent Palindrome Formation

Given a string S of length N (N >= 2). You can choose any index and replace the character at that index with any other character of your choice any number of times, then the task is to minimize the number of operations (including zero), after that, all the characters can't make an S palindrome wh

Minimum number of deletions to make a string palindrome | Set 2

Given a string A, compute the minimum number of characters you need to delete to make resulting string a palindrome. Examples: Input : baca Output : 1 Input : geek Output : 2 We have discussed one approach in below post. Minimum number of deletions to make a string palindrome Below approach will use

Minimum Count of Bit flips required to make a Binary String Palindromic

Given an integer N, the task is to find the minimum number of bits required to be flipped to convert the binary representation of N into a palindrome. Examples: Input: N = 12 Output: 2 Explanation: Binary String representing 12 = "1100". To make "1100" a palindrome, convert the string to "0110". The

Generate number with given operation and check if it is palindrome

Given an integer N the task is to create a string out of it by repeating the number such that the length of the resultant string is equal to the sum of the digits in the original number. For eg: If the number is 61 and the sum of the digits is 6 + 1 = 7 so the string generated after repeating 61 wil