Isomorphic Words

Class

public class IsomorphicWords { public int countPairs(String[] words) { // fill in code here } }

Problem Statement

Two words are called isomorphic if the letters in one word can be remapped to get the second word. Remapping a letter means replacing all occurrences of it with another letter. The ordering of the letters remains unchanged. No two letters may map to the same letter, but a letter may map to itself.

For example, the words "abca" and "zbxz" are isomorphic because we can map 'a' to 'z', 'b' to 'b' and 'c' to 'x'.

Given a String[] words, return how many (unordered) pairs of words are isomorphic.

Constraints

words will contain between 2 and 50 elements, inclusive.
Each element of words will contain between 1 and 50 lowercase letters ('a'-'z'), inclusive.
All elements of words will have the same length.
There will be no duplicates in words.

Examples

```
{"abca", "zbxz", "opqr"}

Returns: 1
```
"abca" and "zbxz" are isomorphic, but none of the two is isomorphic with "opqr".
```
{"aa", "ab", "bb", "cc", "cd"}

Returns: 4
```
The four isomorphic pairs are {"aa", "bb"}, {"aa", "cc"}, {"bb", "cc"} and {"ab", "cd"}.


{ "cacccdaabc", "cdcccaddbc", "dcdddbccad", "bdbbbaddcb",
  "bdbcadbbdc", "abaadcbbda", "babcdabbac", "cacdbaccad",
  "dcddabccad", "cacccbaadb", "bbcdcbcbdd", "bcbadcbbca" }

Returns: 13

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