# Make all characters of a string same by minimum number of increments or decrements of ASCII values of characters

• Last Updated : 29 Apr, 2021

Given a string S of length N, the task is to make all characters of the string the same by incrementing/decrementing the ASCII value of any character by 1 any number of times.
Note: All characters must be changed to a character of the original string.

Examples:

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Input: S = “geeks”
Output: 20
Explanation:
The minimum number of operations can be attained by making all the characters of the string equal to ‘g’.
Increment ASCII value of 2 ‘e’s by 2.
Decrement ASCII value of ‘k’ by 4,
Decrement ASCII value of ‘s’ by 12.
Hence, the number of operations required = 2 + 2 + 4 + 12 = 20

Input: S = “cake”
Output: 12
Explanation:
The minimum number of operations can be attained by making all the characters of the string equal to ‘c’.
Increment ASCII value of ‘a’ by 2.
Decrement ASCII value of ‘e’ by 2.
Decrement ASCII value of ‘k’ by 8.
Hence, number of operations required = 2 + 2 + 8 = 12

Naive approach: The simplest approach to solve the problem is to traverse the string and for each distinct character, calculate the total number of operations required to make all characters of the string the same as that character. Finally, print the minimum number of operations required for any character.
Time complexity: O(N2)
Auxiliary Space: O(1)

Efficient approach: The above approach can be optimized by making an observation that the minimum number of operations can be attained only if the characters are made equal to the median character in a sorted string.
Follow the steps below to solve the problem:

• Sort characters of the string in non-decreasing order.
• Now, to make all characters equal with minimum number of operations, make the characters equal to the character at the middle of the sorted string.
• Find the character at the middle of the sorted string as mid = S[N / 2].
• Initialize a variable, say total_operations, to store the minimum number of operations required to make all characters of the string equal.
• Traverse the string and for each character encountered, update total_operations by adding the absolute difference of current character and mid.
• Print total_operations as the minimum number of operations required.

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach` `#include ``using` `namespace` `std;` `// Function to check if all characters``// of the string can be made the same``int` `sameChar(string S, ``int` `N)``{` `    ``// Sort the string``    ``sort(S.begin(), S.end());` `    ``// Calculate ASCII value``    ``// of the median character``    ``int` `mid = S[N / 2];` `    ``// Stores the minimum number of``    ``// operations required to make``    ``// all characters equal``    ``int` `total_operations = 0;` `    ``// Traverse the string``    ``for` `(``int` `i = 0; i < N; i++) {` `        ``// Calculate absolute value of``        ``// current character and median character``        ``total_operations``            ``+= ``abs``(``int``(S[i]) - mid);``    ``}` `    ``// Print the minimum number of``    ``// operations required``    ``cout << total_operations;``}` `// Driver Code``int` `main()``{``    ``string S = ``"geeks"``;``    ``int` `N = S.size();` `    ``sameChar(S, N);` `    ``return` `0;``}`

## Java

 `// Java program for the above approach``import` `java.io.*;``import` `java.util.Arrays;``class` `GFG {` `  ``// Function to check if all characters``  ``// of the string can be made the same``  ``static` `void` `sameChar(String S, ``int` `N)``  ``{` `    ``char` `temp[] = S.toCharArray();` `    ``// Sort the string``    ``Arrays.sort(temp);` `    ``String s = ``new` `String(temp);` `    ``// Calculate ASCII value``    ``// of the median character``    ``int` `mid = s.charAt(N / ``2``);` `    ``// Stores the minimum number of``    ``// operations required to make``    ``// all characters equal``    ``int` `total_operations = ``0``;` `    ``// Traverse the string``    ``for` `(``int` `i = ``0``; i < N; i++) {` `      ``// Calculate absolute value of``      ``// current character and median character``      ``total_operations``        ``+= Math.abs(((s.charAt(i) - ``0``) - mid));``    ``}` `    ``// Print the minimum number of``    ``// operations required``    ``System.out.print(total_operations);``  ``}` `  ``// Driver Code``  ``public` `static` `void` `main(String[] args)``  ``{``    ``String S = ``"geeks"``;``    ``int` `N = S.length();` `    ``sameChar(S, N);``  ``}``}` `// This code is contributed by Dharanendra L V.`

## Python3

 `# Python program for the above approach` `# Function to check if all characters``# of the string can be made the same``def` `sameChar(S, N):` `    ``# Sort the string``    ``S ``=` `''.join(``sorted``(S))` `    ``# Calculate ASCII value``    ``# of the median character``    ``mid ``=` `ord``(S[N ``/``/` `2``])` `    ``# Stores the minimum number of``    ``# operations required to make``    ``# all characters equal``    ``total_operations ``=` `0` `    ``# Traverse the string``    ``for` `i ``in` `range``(N):` `        ``# Calculate absolute value of``        ``# current character and median character``        ``total_operations ``+``=` `abs``(``ord``(S[i]) ``-` `mid)` `    ``# Print the minimum number of``    ``# operations required``    ``print``(total_operations)` `# Driver Code``S ``=` `"geeks"``N ``=` `len``(S)``sameChar(S, N)` `# This code is contributed by subhammahato348.`

## C#

 `// C# program for the above approach``using` `System;``public` `class` `GFG {` `  ``// Function to check if all characters``  ``// of the string can be made the same``  ``static` `void` `sameChar(String S, ``int` `N)``  ``{` `    ``char``[] temp = S.ToCharArray();` `    ``// Sort the string``    ``Array.Sort(temp);` `    ``String s = ``new` `String(temp);` `    ``// Calculate ASCII value``    ``// of the median character``    ``int` `mid = s[N / 2];` `    ``// Stores the minimum number of``    ``// operations required to make``    ``// all characters equal``    ``int` `total_operations = 0;` `    ``// Traverse the string``    ``for` `(``int` `i = 0; i < N; i++) {` `      ``// Calculate absolute value of``      ``// current character and median character``      ``total_operations += Math.Abs((s[i] - 0) - mid);``    ``}` `    ``// Print the minimum number of``    ``// operations required``    ``Console.Write(total_operations);``  ``}` `  ``// Driver Code``  ``static` `public` `void` `Main()``  ``{` `    ``String S = ``"geeks"``;``    ``int` `N = S.Length;` `    ``sameChar(S, N);``  ``}``}` `// This code is contributed by Dharanendra L V.`

## Javascript

 ``

Output:
`20`

Time Complexity: O(N * log(N))
Auxiliary Space: O(1)

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