**Rotation Groups - Amazon Top Interview Questions**

### Problem Statement :

A rotation group for a string contains all of its unique rotations. For example, "123" can be rotated to "231" and "312" and they are all in the same rotation group. Given a list of strings words, group each word by their rotation group, and return the total number of groups. Constraints n ≤ 200 where n is the length of words. Example 1 Input words = ["abc", "xy", "yx", "z", "bca"] Output 3 Explanation There are three rotation groups: ["abc", "bca"] ["xy", "yx"] ["z"]

### Solution :

` ````
Solution in C++ :
int solve(vector<string>& words) {
unordered_set<string> vis;
for (string& s : words) {
for (int i = 0; i < s.size(); i++) {
rotate(s.begin(), s.begin() + 1, s.end());
if (vis.count(s)) break;
}
vis.insert(s);
}
return vis.size();
}
```

` ````
Solution in Java :
import java.util.*;
class Solution {
public int solve(String[] words) {
ArrayList<String> set = new ArrayList<>();
for (String word : words) {
boolean exist = false;
for (String rotation : set) {
if (rotation.length() == word.length() * 2 && rotation.contains(word)) {
exist = true;
break;
}
}
if (!exist) {
set.add(word + word);
}
}
return set.size();
}
}
```

` ````
Solution in Python :
class Solution:
def solve(self, words):
s = set()
for ind in range(len(words)):
c = words[ind]
for i in s:
if len(c) == len(i) and c in i * 2:
break
else:
s.add(c)
return len(s)
```

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