codeforces#P1045I. Palindrome Pairs
Palindrome Pairs
Description
After learning a lot about space exploration, a little girl named Ana wants to change the subject.
Ana is a girl who loves palindromes (string that can be read the same backwards as forward). She has learned how to check for a given string whether it's a palindrome or not, but soon she grew tired of this problem, so she came up with a more interesting one and she needs your help to solve it:
You are given an array of strings which consist of only small letters of the alphabet. Your task is to find how many palindrome pairs are there in the array. A palindrome pair is a pair of strings such that the following condition holds: at least one permutation of the concatenation of the two strings is a palindrome. In other words, if you have two strings, let's say "aab" and "abcac", and you concatenate them into "aababcac", we have to check if there exists a permutation of this new string such that it is a palindrome (in this case there exists the permutation "aabccbaa").
Two pairs are considered different if the strings are located on different indices. The pair of strings with indices $(i,j)$ is considered the same as the pair $(j,i)$.
The first line contains a positive integer $N$ ($1 \le N \le 100\,000$), representing the length of the input array.
Eacg of the next $N$ lines contains a string (consisting of lowercase English letters from 'a' to 'z') — an element of the input array.
The total number of characters in the input array will be less than $1\,000\,000$.
Output one number, representing how many palindrome pairs there are in the array.
Input
The first line contains a positive integer $N$ ($1 \le N \le 100\,000$), representing the length of the input array.
Eacg of the next $N$ lines contains a string (consisting of lowercase English letters from 'a' to 'z') — an element of the input array.
The total number of characters in the input array will be less than $1\,000\,000$.
Output
Output one number, representing how many palindrome pairs there are in the array.
Samples
3
aa
bb
cd
1
6
aab
abcac
dffe
ed
aa
aade
6
Note
The first example:
- aa $+$ bb $\to$ abba.
The second example:
- aab $+$ abcac $=$ aababcac $\to$ aabccbaa
- aab $+$ aa $=$ aabaa
- abcac $+$ aa $=$ abcacaa $\to$ aacbcaa
- dffe $+$ ed $=$ dffeed $\to$ fdeedf
- dffe $+$ aade $=$ dffeaade $\to$ adfaafde
- ed $+$ aade $=$ edaade $\to$ aeddea