[LeetCode]#893. Groups of Special-Equivalent Strings

Environment: Python 3.8

Key technique: set

You are given an array A of strings.

A move onto S consists of swapping any two even indexed characters of S, or any two odd indexed characters of S.

Two strings S and T are special-equivalent if after any number of moves onto S, S == T.

For example, S = "zzxy" and T = "xyzz" are special-equivalent because we may make the moves "zzxy" -> "xzzy" -> "xyzz" that swap S[0] and S[2], then S[1] and S[3].

Now, a group of special-equivalent strings from A is a non-empty subset of A such that:

1. Every pair of strings in the group are special equivalent, and;
2. The group is the largest size possible (ie., there isn’t a string S not in the group such that S is special equivalent to every string in the group)

Return the number of groups of special-equivalent strings from A.

Example 1:

Input: ["abcd","cdab","cbad","xyzz","zzxy","zzyx"]
Output: 3
Explanation: 
One group is ["abcd", "cdab", "cbad"], since they are all pairwise special equivalent, and none of the other strings are all pairwise special equivalent to these.
The other two groups are ["xyzz", "zzxy"] and ["zzyx"].  Note that in particular, "zzxy" is not special equivalent to "zzyx".

Example 2:

Input: ["abc","acb","bac","bca","cab","cba"]
Output: 3

Analysis:

1. Move abcd as two pair ac + bd.
2. Sort it and is acbd.
3. Check other A[i] is match or not.
4. Return all result numbers.

Solution:

class Solution():
    def numSpecialEquivGroups(self, A):
ans = set()
        for a in A:
            ans.add(''.join(sorted(a[0::2])) + ''.join(sorted(a[1::2])))
        return len(ans)

Submissions:

Reference:

https://blog.csdn.net/fuxuemingzhu/article/details/82083609