message: Update sentence-similarity-ii.cpp
diff: @@ -11,10 +11,10 @@ public:
  UnionFind union_find(2 * pairs.size());
  for (const auto& pair : pairs) {
  if (!lookup.count(pair.first)) {
  - lookup[pair.first] = lookup.size() - 1;
  + lookup.emplace(pair.first, lookup.size());
  }
  if (!lookup.count(pair.second)) {
  - lookup[pair.second] = lookup.size() - 1;
  + lookup.emplace(pair.second, lookup.size());
  }
  union_find.union_set(lookup[pair.first], lookup[pair.second]);
  }
  