Given a string and a number k, find the longest subsequence of a string where every character appears at-least k times.
Input : str = "geeksforgeek" k = 2 Output : geeskgeeks Every character in the output subsequence appears at-least 2 times. Input : str = "aabbaabacabb" k = 5 Output : aabbaabaabb
Method 1 (Brute force)
We generate all subsequences. For every subsequence count distinct characters in it and find the longest subsequence where every character appears at-least k times.
Method 2 (Efficient way)
1. Find the frequency of the string and store it in an integer array of size 26 representing the alphabets.
2. After finding the frequency iterate the string character by character and if the frequency of that character is greater than or equal to the required number of repetitions then print that character then and there only.
This code has a time complexity of O(n) where n is the size of the string.
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