# Group all occurrences of characters according to first appearance

Given a string of lowercase characters, the task is to print the string in a manner such that a character comes first in string displays first with all its occurrences in string.

Examples:

```Input : str = "geeksforgeeks"
Output:  ggeeeekkssfor
Explanation: In the given string 'g' comes first
and occurs 2 times so it is printed first
Then 'e' comes in this string and 4 times so
it gets printed. Similarly remaining string is
printed.

Input :  str = "occurrence"
output : occcurreen

Input  : str = "cdab"
Output : cdab
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

This problem is a string version of following problem for array of integers.

Group multiple occurrence of array elements ordered by first occurrences

Since given strings have only 26 possible characters, it is easier to implement for strings.

Implementation:
1- Count the occurrence of all the characters in given string using an array of size 26.
2- Then start traversing the string. Print every character its count times.

## C++

 `// C++ program to print all occurrences of every character ` `// together. ` `# include ` `using` `namespace` `std; ` ` `  `// Since only lower case characters are there ` `const` `int` `MAX_CHAR = 26; ` ` `  `// Function to print the string ` `void` `printGrouped(string str) ` `{ ` `    ``int` `n = str.length(); ` ` `  `    ``// Initialize counts of all characters as 0 ` `    ``int`  `count[MAX_CHAR] = {0}; ` ` `  `    ``// Count occurrences of all characters in string ` `    ``for` `(``int` `i = 0 ; i < n ; i++) ` `        ``count[str[i]-``'a'``]++; ` ` `  `    ``// Starts traversing the string ` `    ``for` `(``int` `i = 0; i < n ; i++) ` `    ``{ ` `        ``// Print the character till its count in ` `        ``// hash array ` `        ``while` `(count[str[i]-``'a'``]--) ` `            ``cout << str[i]; ` ` `  `        ``// Make this character's count value as 0. ` `        ``count[str[i]-``'a'``] = 0; ` `    ``} ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``string str = ``"geeksforgeeks"``; ` ` `  `    ``printGrouped(str); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to print all occurrences of every character ` `// together. ` ` `  `class` `Test ` `{ ` `    ``// Since only lower case characters are there ` `    ``static` `final` `int` `MAX_CHAR = ``26``; ` `     `  `    ``// Method to print the string ` `    ``static` `void` `printGrouped(String str) ` `    ``{ ` `        ``int` `n = str.length(); ` `      `  `        ``// Initialize counts of all characters as 0 ` `        ``int`  `count[] = ``new` `int``[MAX_CHAR]; ` `      `  `        ``// Count occurrences of all characters in string ` `        ``for` `(``int` `i = ``0` `; i < n ; i++) ` `            ``count[str.charAt(i)-``'a'``]++; ` `      `  `        ``// Starts traversing the string ` `        ``for` `(``int` `i = ``0``; i < n ; i++) ` `        ``{ ` `            ``// Print the character till its count in ` `            ``// hash array ` `            ``while` `(count[str.charAt(i)-``'a'``]!=``0``){ ` `                ``System.out.print(str.charAt(i)); ` `                ``count[str.charAt(i)-``'a'``]--; ` `            ``} ` `      `  `            ``// Make this character's count value as 0. ` `            ``count[str.charAt(i)-``'a'``] = ``0``; ` `        ``} ` `    ``} ` `     `  `    ``// Driver method ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``String str = ``new` `String(``"geeksforgeeks"``); ` `          `  `        ``printGrouped(str); ` `    ``} ` `} `

## Python3

 `# Python3 program to print all occurrences ` `# of every character together. ` ` `  `# Since only lower case characters are there ` `MAX_CHAR ``=` `26` ` `  `# Function to print the string ` `def` `printGrouped(string): ` `    ``n ``=` `len``(string) ` ` `  `    ``# Initialize counts of all characters as 0 ` `    ``count ``=` `[``0``] ``*` `MAX_CHAR ` ` `  `    ``# Count occurrences of all characters in string ` `    ``for` `i ``in` `range``(n): ` `        ``count[``ord``(string[i]) ``-` `ord``(``"a"``)] ``+``=` `1` ` `  `    ``# Starts traversing the string ` `    ``for` `i ``in` `range``(n): ` ` `  `        ``# Print the character till its count in ` `        ``# hash array ` `        ``while` `count[``ord``(string[i]) ``-` `ord``(``"a"``)]: ` `            ``print``(string[i], end ``=` `"") ` `            ``count[``ord``(string[i]) ``-` `ord``(``"a"``)] ``-``=` `1` ` `  `        ``# Make this character's count value as 0. ` `        ``count[``ord``(string[i]) ``-` `ord``(``"a"``)] ``=` `0` ` `  `# Driver code ` `if` `__name__ ``=``=` `"__main__"``: ` `    ``string ``=` `"geeksforgeeks"` `    ``printGrouped(string) ` ` `  `# This code is contributed by ` `# sanjeev2552 `

## C#

 `// C# program to print all  ` `// occurrences of every  ` `// character together. ` `using` `System; ` ` `  `class` `GFG ` `{ ` `    ``// Since only lower case  ` `    ``// characters are there ` `    ``static` `int` `MAX_CHAR = 26; ` `     `  `    ``// Method to print  ` `    ``// the string ` `    ``static` `void` `printGrouped(String str) ` `    ``{ ` `        ``int` `n = str.Length; ` `     `  `        ``// Initialize counts of ` `        ``// all characters as 0 ` `        ``int` `[]count = ``new` `int``[MAX_CHAR]; ` `     `  `        ``// Count occurrences of  ` `        ``// all characters in string ` `        ``for` `(``int` `i = 0 ; i < n ; i++) ` `            ``count[str[i] - ``'a'``]++; ` `     `  `        ``// Starts traversing ` `        ``// the string ` `        ``for` `(``int` `i = 0; i < n ; i++) ` `        ``{ ` `            ``// Print the character  ` `            ``// till its count in ` `            ``// hash array ` `            ``while` `(count[str[i] - ``'a'``] != 0) ` `            ``{ ` `                ``Console.Write(str[i]); ` `                ``count[str[i] - ``'a'``]--; ` `            ``} ` `     `  `            ``// Make this character's  ` `            ``// count value as 0. ` `            ``count[str[i] - ``'a'``] = 0; ` `        ``} ` `    ``} ` `     `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``string` `str = ``"geeksforgeeks"``; ` `        ``printGrouped(str); ` `    ``} ` `} ` ` `  `// This code is contributed by Sam007 `

Output:

```ggeeeekkssfor
```

This article is contributed by Sahil Chhabra. 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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Improved By : Sam007, sanjeev2552

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