Package g2001_2100.s2014_longest_subsequence_repeated_k_times

Class Solution

  • public class Solution
extends Object
    2014 - Longest Subsequence Repeated k Times.

    Hard

    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.

    • For example, "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 "**b**a**bab**c**ba**".

    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:

    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.length
    • 2 <= n, k <= 2000
    • 2 <= n < k * 8
    • s consists of lowercase English letters.

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • longestSubsequenceRepeatedK

        public String longestSubsequenceRepeatedK​(String s,
                                          int k)