**Problem Statement:**
Given the required input arguments, write an efficient algorithm to solve the **Happy Number** problem. Implement the required logic as specified by standard definitions for this classic algorithmic challenge.
**Hint / Expected Approach:**
Sum of digit squares; detect cycle via slow/fast
**Edge Cases to Consider:**
- (1) n = 1 (already happy)
- (2) n = 7 (happy after steps)
- (3) Known sad number (e.g. 4)