Watch 10 video solutions for Longest Subsequence Repeated k Times, a hard level problem involving String, Backtracking, Greedy. This walkthrough by Abdul Bari has 1,257,418 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
You are given a string s of length n, and an integer k. You are tasked to find the longest subsequence repeated k times in string s.
A subsequence is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters.
A subsequence seq is repeated k times in the string s if seq * k is a subsequence of s, where seq * k represents a string constructed by concatenating seq k times.
"bba" is repeated 2 times in the string "bababcba", because the string "bbabba", constructed by concatenating "bba" 2 times, is a subsequence of the string "bababcba".Return the longest subsequence repeated k times in string s. If multiple such subsequences are found, return the lexicographically largest one. If there is no such subsequence, return an empty string.
Example 1:
Input: s = "letsleetcode", k = 2 Output: "let" Explanation: There are two longest subsequences repeated 2 times: "let" and "ete". "let" is the lexicographically largest one.
Example 2:
Input: s = "bb", k = 2 Output: "b" Explanation: The longest subsequence repeated 2 times is "b".
Example 3:
Input: s = "ab", k = 2 Output: "" Explanation: There is no subsequence repeated 2 times. Empty string is returned.
Constraints:
n == s.length2 <= n, k <= 20002 <= n < k * 8s consists of lowercase English letters.