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Find the count of palindromic sub-string of a string in its sorted form
• Difficulty Level : Easy
• Last Updated : 30 Apr, 2021

Given a string str consisting of lowercase English alphabets, the task is to find the total number of palindromic sub-strings present in the sorted form of str.
Examples:

Input: str = “acbbd”
Output:
All palindromic sub-string in it’s sorted form (“abbcd”) are “a”, “b”, “b”, “bb”, “c” and “d”.
Input: str = “abbabdbd”
Output: 16

Naive approach: One way is to sort the given string and then count the total number of sub-strings present which are palindromes. For finding number of palindromic sub-strings this approach can be used which has time complexity of O(n^2).
Optimized approach: An efficient way is to count the frequency of each character and then for each frequency total number of palindromes will (n*(n+1))/2 as all the palindromic sub-strings of a sorted string will consist of the same character.
For example, palindromic sub-string for the string “aabbbcd” will be “a”, “aa”, …, “bbb”, “c”, … etc. Time complexity for this approach will be O(n).

• Create a hash table for storing the frequencies of each character of the string str.
• Traverse the hash table and for each non-zero frequency add (hash[i] * (hash[i]+1)) / 2 to the sum.
• Print the sum in the end.

Below is the implementation of the above approach:

## C++

 `// CPP program to find the count of palindromic sub-string``// of a string in it's ascending form``#include ``using` `namespace` `std;` `const` `int` `MAX_CHAR = 26;` `// function to return count of palindromic sub-string``int` `countPalindrome(string str)``{``    ``int` `n = str.size();``    ``int` `sum = 0;` `    ``// calculate frequency``    ``int` `hashTable[MAX_CHAR];``    ``for` `(``int` `i = 0; i < n; i++)``        ``hashTable[str[i] - ``'a'``]++;` `    ``// calculate count of palindromic sub-string``    ``for` `(``int` `i = 0; i < 26; i++) {``        ``if` `(hashTable[i])``            ``sum += (hashTable[i] * (hashTable[i] + 1) / 2);``    ``}` `    ``// return result``    ``return` `sum;``}` `// driver program``int` `main()``{``    ``string str = ``"ananananddd"``;` `    ``cout << countPalindrome(str);``    ``return` `0;``}`

## Java

 `// Java program to find the count of palindromic sub-string``// of a string in it's ascending form` `class` `GFG {` `    ``final` `static` `int` `MAX_CHAR = ``26``;` `// function to return count of palindromic sub-string``    ``static` `int` `countPalindrome(String str) {``        ``int` `n = str.length();``        ``int` `sum = ``0``;` `        ``// calculate frequency``        ``int` `hashTable[] = ``new` `int``[MAX_CHAR];``        ``for` `(``int` `i = ``0``; i < n; i++) {``            ``hashTable[str.charAt(i) - ``'a'``]++;``        ``}` `        ``// calculate count of palindromic sub-string``        ``for` `(``int` `i = ``0``; i < ``26``; i++) {``            ``if` `(hashTable[i] != ``0``) {``                ``sum += (hashTable[i] * (hashTable[i] + ``1``) / ``2``);``            ``}``        ``}` `        ``// return result``        ``return` `sum;``    ``}` `// driver program``    ``public` `static` `void` `main(String[] args) {``        ``String str = ``"ananananddd"``;` `        ``System.out.println(countPalindrome(str));` `    ``}``}`

## Python3

 `# Python3 program to find the count of``# palindromic sub-string of a string``# in it's ascending form``MAX_CHAR ``=` `26` `# function to return count of``# palindromic sub-string``def` `countPalindrome(``str``):` `    ``n ``=` `len` `(``str``)``    ``sum` `=` `0` `    ``# calculate frequency``    ``hashTable ``=` `[``0``] ``*` `MAX_CHAR``    ``for` `i ``in` `range``(n):``        ``hashTable[``ord``(``str``[i]) ``-``                  ``ord``(``'a'``)] ``+``=` `1` `    ``# calculate count of palindromic``    ``# sub-string``    ``for` `i ``in` `range``(``26``) :``        ``if` `(hashTable[i]):``            ``sum` `+``=` `(hashTable[i] ``*``                   ``(hashTable[i] ``+` `1``) ``/``/` `2``)` `    ``# return result``    ``return` `sum` `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``str` `=` `"ananananddd"` `    ``print` `(countPalindrome(``str``))` `# This code is contributed by ita_c`

## C#

 `// C# program to find the count of palindromic sub-string``// of a string in it's ascending form``using` `System;``                    ` `public` `class` `GFG{`` ` `    ``readonly` `static` `int` `MAX_CHAR = 26;`` ` `// function to return count of palindromic sub-string``    ``static` `int` `countPalindrome(String str) {``        ``int` `n = str.Length;``        ``int` `sum = 0;`` ` `        ``// calculate frequency``        ``int` `[]hashTable = ``new` `int``[MAX_CHAR];``        ``for` `(``int` `i = 0; i < n; i++) {``            ``hashTable[str[i] - ``'a'``]++;``        ``}`` ` `        ``// calculate count of palindromic sub-string``        ``for` `(``int` `i = 0; i < 26; i++) {``            ``if` `(hashTable[i] != 0) {``                ``sum += (hashTable[i] * (hashTable[i] + 1) / 2);``            ``}``        ``}`` ` `        ``// return result``        ``return` `sum;``    ``}`` ` `// driver program``    ``public` `static` `void` `Main() {``        ``String str = ``"ananananddd"``;`` ` `        ``Console.Write(countPalindrome(str));`` ` `    ``}``}` `// This code is contributed by Rajput-Ji`

## PHP

 ``

## Javascript

 ``
Output:
`26`

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