------
## 最终结论
```python
def is_happy(s):
    if len(s) < 3:
        return False
    
    for i in range(len(s) - 2):
        if s[i] == s[i + 1] or s[i] == s[i + 2] or s[i + 1] == s[i + 2]:
            return False
    
    return True
```