The k-th Lexicographical String of All Happy Strings of Length n.py

class Solution:
    def getHappyString(self, n: int, k: int) -> str:
        ans = []
        letters = ['a','b','c']
        def happystr(n,prev,temp):
            if n==0:
                ans.append("".join(temp))
                return 
            for l in letters: 
                if l!=prev: 
                    happystr(n-1,l,temp+[l])
        happystr(n,"",[])
        if len(ans)<k:
            return ""
        return ans[k-1]