g2001_2100.s2014_longest_subsequence_repeated_k_times

Class Solution

java.lang.Object

g2001_2100.s2014_longest_subsequence_repeated_k_times.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:

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 Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
String	longestSubsequenceRepeatedK(String s, int k)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

longestSubsequenceRepeatedK

public String longestSubsequenceRepeatedK(String s,
                                          int k)