Step 1 - Understand the problem and establish design scope
Candidate: What types of notifications does the system support? Interviewer: Push notification, SMS message, and email. Candidate: Is it a real-time system? Interviewer: Let us say it is a soft …
1.点乘 A ⃗ ⋅ B ⃗ ∣ A ⃗ ∣ ∣ B ⃗ ∣ c o s ⟨ A ⃗ , B ⃗ ⟩ \vec{A} \cdot \vec{B} \left | \vec{A} \right | \left | \vec{B} \right | cos\left \langle \vec{A}, \vec{B} \right \rangle A ⋅B A B cos⟨A ,B ⟩
对应几何意义:向量 A ⃗…