Adding readme file

Author: bugsweeper

Diff for: 1415-Thek-thLexicographicalStringofAllHappyStringsofLengthn/README.md

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+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 of i from 1 to s.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"
+
+
+ 
+Constraints:
+
+
+	1 <= n <= 10
+	1 <= k <= 100
+