message: Update dot-product-of-two-sparse-vectors.cpp
diff: @@ -20,7 +20,7 @@ public:
  int result = 0;
  for (const auto& [i, v] : a->lookup_) {
  if (b->lookup_.count(i)) {
  - result += a->lookup_[i] * b->lookup_[i];
  + result += v * b->lookup_[i];
  }
  }
  return result;
  