1415. The k-th Lexicographical String of All Happy Strings of Length n
https://leetcode.com/problems/the-k-th-lexicographical-string-of-all-happy-strings-of-length-n
Description
A happy string is a string that:
consists only of letters of the set
['a', 'b', 'c']
.s[i] != s[i + 1]
for all values ofi
from1
tos.length - 1
(string is 1-indexed).
For example, strings "abc", "ac", "b" and "abcbabcbcb" are all happy strings and strings "aa", "baa" and "ababbc" are not happy strings.
Given two integers n
and k
, consider a list of all happy strings of length n
sorted in lexicographical order.
Return the kth string of this list or return an empty string if there are less than k
happy strings of length n
.
Example 1:
**Input:** n = 1, k = 3
**Output:** "c"
**Explanation:** The list ["a", "b", "c"] contains all happy strings of length 1. The third string is "c".
Example 2:
**Input:** n = 1, k = 4
**Output:** ""
**Explanation:** There are only 3 happy strings of length 1.
Example 3:
**Input:** n = 3, k = 9
**Output:** "cab"
**Explanation:** There are 12 different happy string of length 3 ["aba", "abc", "aca", "acb", "bab", "bac", "bca", "bcb", "cab", "cac", "cba", "cbc"]. You will find the 9th string = "cab"
Example 4:
**Input:** n = 2, k = 7
**Output:** ""
Example 5:
**Input:** n = 10, k = 100
**Output:** "abacbabacb"
Constraints:
1 <= n <= 10
1 <= k <= 100
ac
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