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Minimum reduce operations to convert a given string into a palindrome
• Difficulty Level : Basic
• Last Updated : 21 May, 2021

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 covered 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.

## C++

 `// CPP program to count minimum reduce``// operations to make a palindrome``#include ``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

 ``

## Javascript

 ``

Output :

`4`

This article is contributed by Sahil Srivastava. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.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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