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# Maximum number of characters between any two same character in a string

• Difficulty Level : Medium
• Last Updated : 21 May, 2021

Given a string, find the maximum number of characters between any two characters in the string. If no character repeats, print -1.

Examples:

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```Input : str = "abba"
Output : 2
The maximum number of characters are
between two occurrences of 'a'.

Input : str = "baaabcddc"
Output : 3
The maximum number of characters are
between two occurrences of 'b'.

Input : str = "abc"
Output : -1```

Approach 1 (Simple): Use two nested loops. The outer loop picks characters from left to right, the inner loop finds the farthest occurrence and keeps track of the maximum.

## C++

 `// Simple C++ program to find maximum number``// of characters between two occurrences of``// same character``#include ``using` `namespace` `std;` `int` `maximumChars(string& str)``{``    ``int` `n = str.length();``    ``int` `res = -1;``    ``for` `(``int` `i = 0; i < n - 1; i++)``        ``for` `(``int` `j = i + 1; j < n; j++)``            ``if` `(str[i] == str[j])``                ``res = max(res, ``abs``(j - i - 1));``    ``return` `res;``}` `// Driver code``int` `main()``{``    ``string str = ``"abba"``;``    ``cout << maximumChars(str);``    ``return` `0;``}`

## Java

 `// Simple Java program to find maximum``// number of characters between two``// occurrences of same character``class` `GFG {``    ` `    ``static` `int` `maximumChars(String str)``    ``{``        ``int` `n = str.length();``        ``int` `res = -``1``;``        ` `        ``for` `(``int` `i = ``0``; i < n - ``1``; i++)``            ``for` `(``int` `j = i + ``1``; j < n; j++)``                ``if` `(str.charAt(i) == str.charAt(j))``                    ``res = Math.max(res,``                         ``Math.abs(j - i - ``1``));``                         ` `        ``return` `res;``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``String str = ``"abba"``;``        ` `        ``System.out.println(maximumChars(str));``    ``}``}` `// This code is contributed by vt_m.`

## Python3

 `# Simple Python3 program to find maximum number``# of characters between two occurrences of``# same character``def` `maximumChars(``str``):``    ``n ``=` `len``(``str``)``    ``res ``=` `-``1``    ``for` `i ``in` `range``(``0``, n ``-` `1``):``        ``for` `j ``in` `range``(i ``+` `1``, n):``            ``if` `(``str``[i] ``=``=` `str``[j]):``                ``res ``=` `max``(res, ``abs``(j ``-` `i ``-` `1``))``    ``return` `res` `# Driver code``if` `__name__ ``=``=` `'__main__'``:``    ``str` `=` `"abba"``    ``print``(maximumChars(``str``))` `# This code is contributed by PrinciRaj1992`

## C#

 `// Simple C# program to find maximum``// number of characters between two``// occurrences of same character``using` `System;` `public` `class` `GFG {``    ` `    ``static` `int` `maximumChars(``string` `str)``    ``{``        ``int` `n = str.Length;``        ``int` `res = -1;``        ` `        ``for` `(``int` `i = 0; i < n - 1; i++)``            ``for` `(``int` `j = i + 1; j < n; j++)``                ``if` `(str[i] == str[j])``                    ``res = Math.Max(res,``                         ``Math.Abs(j - i - 1));``                         ` `        ``return` `res;``    ``}``    ` `    ``// Driver code``    ``static` `public` `void` `Main ()``    ``{``        ``string` `str = ``"abba"``;``        ` `        ``Console.WriteLine(maximumChars(str));``    ``}``}` `// This code is contributed by vt_m.`

## Javascript

 ``

Output:

`2`

Time Complexity : O(n^2)

Approach 2 (Efficient) : Initialize an array”FIRST” of length 26 in which we have to store the first occurrence of an alphabet in the string and another array “LAST” of length 26 in which we will store the last occurrence of the alphabet in the string. Here, index 0 corresponds to alphabet a, 1 for b and so on . After that, we will take the difference between the last and first arrays to find the max difference if they are not at the same position.

## C++

 `// Efficient C++ program to find maximum number``// of characters between two occurrences of``// same character``#include ``using` `namespace` `std;` `const` `int` `MAX_CHAR = 256;` `int` `maximumChars(string& str)``{``    ``int` `n = str.length();``    ``int` `res = -1;` `    ``// Initialize all indexes as -1.``    ``int` `firstInd[MAX_CHAR];``    ``for` `(``int` `i = 0; i < MAX_CHAR; i++)``        ``firstInd[i] = -1;` `    ``for` `(``int` `i = 0; i < n; i++) {``        ``int` `first_ind = firstInd[str[i]];` `        ``// If this is first occurrence``        ``if` `(first_ind == -1)``            ``firstInd[str[i]] = i;` `        ``// Else find distance from previous``        ``// occurrence and update result (if``        ``// required).``        ``else``            ``res = max(res, ``abs``(i - first_ind - 1));``    ``}``    ``return` `res;``}` `// Driver code``int` `main()``{``    ``string str = ``"abba"``;``    ``cout << maximumChars(str);``    ``return` `0;``}`

## Java

 `// Efficient java program to find maximum``// number of characters between two``// occurrences of same character``import` `java.io.*;` `public` `class` `GFG {` `    ``static` `int` `MAX_CHAR = ``256``;``    ` `    ``static` `int` `maximumChars(String str)``    ``{``        ``int` `n = str.length();``        ``int` `res = -``1``;``    ` `        ``// Initialize all indexes as -1.``        ``int` `[]firstInd = ``new` `int``[MAX_CHAR];``        ` `        ``for` `(``int` `i = ``0``; i < MAX_CHAR; i++)``            ``firstInd[i] = -``1``;``    ` `        ``for` `(``int` `i = ``0``; i < n; i++)``        ``{``            ``int` `first_ind = firstInd[str.charAt(i)];``    ` `            ``// If this is first occurrence``            ``if` `(first_ind == -``1``)``                ``firstInd[str.charAt(i)] = i;``    ` `            ``// Else find distance from previous``            ``// occurrence and update result (if``            ``// required).``            ``else``                ``res = Math.max(res, Math.abs(i``                                  ``- first_ind - ``1``));``        ``}``        ` `        ``return` `res;``    ``}``    ` `    ``// Driver code``    ` `    ``static` `public` `void` `main (String[] args)``    ``{``        ``String str = ``"abba"``;``        ` `        ``System.out.println(maximumChars(str));``    ``}``}` `// This code is contributed by vt_m.`

## Python3

 `# Efficient Python3 program to find maximum``# number of characters between two occurrences``# of same character` `MAX_CHAR ``=` `256` `def` `maximumChars(str1):` `    ``n ``=` `len``(str1)``    ``res ``=` `-``1` `    ``# Initialize all indexes as -1.``    ``firstInd ``=` `[``-``1` `for` `i ``in` `range``(MAX_CHAR)]` `    ``for` `i ``in` `range``(n):``        ``first_ind ``=` `firstInd[``ord``(str1[i])]` `        ``# If this is first occurrence``        ``if` `(first_ind ``=``=` `-``1``):``            ``firstInd[``ord``(str1[i])] ``=` `i` `        ``# Else find distance from previous``        ``# occurrence and update result (if``        ``# required).``        ``else``:``            ``res ``=` `max``(res, ``abs``(i ``-` `first_ind ``-` `1``))``    ` `    ``return` `res` `# Driver code``str1 ``=` `"abba"``print``(maximumChars(str1))` `# This code is contributed by Mohit kumar 29`

## C#

 `// Efficient C# program to find maximum``// number of characters between two``// occurrences of same character``using` `System;` `public` `class` `GFG {` `    ``static` `int` `MAX_CHAR = 256;``    ` `    ``static` `int` `maximumChars(``string` `str)``    ``{``        ``int` `n = str.Length;``        ``int` `res = -1;``    ` `        ``// Initialize all indexes as -1.``        ``int` `[]firstInd = ``new` `int``[MAX_CHAR];``        ` `        ``for` `(``int` `i = 0; i < MAX_CHAR; i++)``            ``firstInd[i] = -1;``    ` `        ``for` `(``int` `i = 0; i < n; i++)``        ``{``            ``int` `first_ind = firstInd[str[i]];``    ` `            ``// If this is first occurrence``            ``if` `(first_ind == -1)``                ``firstInd[str[i]] = i;``    ` `            ``// Else find distance from previous``            ``// occurrence and update result (if``            ``// required).``            ``else``                ``res = Math.Max(res, Math.Abs(i``                              ``- first_ind - 1));``        ``}``        ` `        ``return` `res;``    ``}``    ` `    ``// Driver code` `    ``static` `public` `void` `Main ()``    ``{``        ``string` `str = ``"abba"``;``        ` `        ``Console.WriteLine(maximumChars(str));``    ``}``}` `// This code is contributed by vt_m.`

## Javascript

 ``

Output:

`2`

Time Complexity : O(n)