Swiggy OA SDE Intern + Fulltime + Fresher + Experienced | CTC - 15 to 30 L | Set 4

Question

Question 3: Mirror Personalities

Problem Statement

N people live in a town. The houses are arranged in a row. The personality of each owner is represented by a lowercase English character. Each person is in a fight with all those people who have a mirror personality to the one in the fight.

Let A be the string "abcd...yz". Let B be the reverse of string A, i.e., "zyx...ba". The mirror of any character from string A is the character in the same index in string B.

 * Reverse of 'a' is 'z'.

 * Reverse of 'z' is 'a'.

 * Reverse of 'x' is 'c'.

Given the personality of each person in the town, determine the number of pairs of residents who are in a fight.

Note: Pair (i, j) is the same as (j, i).

Input Format

 * The first line contains N denoting the length of the string.

 * The second line contains S denoting the input string (personalities).

Output Format

 * Return an integer denoting the number of mirror pairs.

Constraints

 * * S[i] is a valid small case English character.

Sample Input

3

aaz

 

Sample Output

2

 

Explanation

Considering 0-based indexing:

 * Person at index 0 is 'a'. Mirror is 'z'. Person at index 2 is 'z'. Pair (0, 2) is valid.

 * Person at index 1 is 'a'. Mirror is 'z'. Person at index 2 is 'z'. Pair (1, 2) is

valid.

 * Total pairs: 2.