1415. The k-th Lexicographical String of All Happy Strings of Length n
Medium
30 Points
String
Backtracking
A happy string is a string that:
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.
Examples
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"
Constraints
1 <= n <= 10
1 <= k <= 100
1415. The k-th Lexicographical String of All Happy Strings of Length n
Medium
30 Points
String
Backtracking
A happy string is a string that:
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.
Examples
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"
Constraints
1 <= n <= 10
1 <= k <= 100
The k-th Lexicographical String of All Happy Strings of Length n - Practice Coding | SlaveCode