refactor(strings, similar-string-groups): add length check

Author: BrianLusina

datastructures/sets/union_find/__init__.py

@@ -22,8 +22,8 @@ def union(self, i: int, j: int) -> bool:
         Merges the sets containing elements 'i' and 'j'.
         Returns True if a merge occurred, False if they were already in the same set.
         """
-        root_i = self.find(i) # 0
-        root_j = self.find(j) # 1
+        root_i = self.find(i)
+        root_j = self.find(j)
 
         if root_i != root_j:
             # Union by rank: attach the smaller tree to the larger tree

pystrings/similar_string_groups/__init__.py

@@ -67,7 +67,10 @@ def are_similar(s1, s2):
 
 def num_similar_groups_2(strs: List[str]) -> int:
     n = len(strs)
-    uf = DisjointSetUnion(n)
+    if n == 0:
+        return 0
+
+    uf = UnionFind(n)
 
     for i in range(n):
         for j in range(i + 1, n):