Given a string ‘s’ and an integer k, find other string ‘t’ such that ‘t’ is the largest subsequence of given string ‘s’ and each character of ‘t’ must occur at least k times in string s.
Input : s = "geeksforgeeks" k = 2 Output : geeksgeeks Input : s = "baaabaacba" k = 3 Output : baaabaaba
A simple solution is to generate all subsequences. For every subsequence, check if it has all characters at least k times. Find longest such subsequence. Time complexity of this approach is exponential.
Efficient Approach We can take another array to keep the record of count of each character from string s, if any character occurred more than or equal to k times, then we simply print it.
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Improved By : Sam007