In this problem, we need to find the length of the longest subsequence having the same left and right rotations. We can solve the problem using the brute-force approach, finding all possible subsequences of the given string and checking each subsequence one by one to see if it has the same left and right rotation. We find the maximum length of such subsequence. The problem with this approach is that it is very time-consuming as its time complexity is O(2N). So, we will learn to write optimized code in this approach. Problem statement – We have given string str containing ... Read More

In this problem, we need to find the last palindrome string in the array. If any string is the same in reading, either we start to read from the start or end, we can say the string is a palindrome. We can compare the starting and ending characters to check whether the particular string is palindromic. Another way to find the palindromic string is to reverse the string and compare it with the original string. Problem statement – We have given an array of length N containing the different strings. We need to find the last palindrome string in the ... Read More

In this problem, we need to find all missing binary strings of length N from the array. We can solve the problem by finding all permutations of a binary string of length N and checking which permutations are absent in the array. Here, we will see iterative and recursive approaches to solve the problem. Problem statement – We have given an array arr[] of different lengths containing the binary strings of length N. We need to find all the missing binary strings of length N from the array. Sample examples Input – arr = {"111", "001", "100", "110"}, N = ... Read More

In this problem, we need to count the total number of substrings of string str containing exactly K distinct vowels. We can solve the problem in two different ways. The first approach is to traverse all substrings and count the number of vowels in each substring. We can also use the map data structure to optimize the code of the first approach. Problem statement – We have given string str of length N. The string contains uppercase and lowercase alphabetical characters. Also, we have given integer K. We need to find the total number of substrings of str containing exactly ... Read More

In this problem, we need to find a total number of substrings of length K containing exactly K vowels. We will see two different approaches to solving the problem. We can use a naïve approach that checks the number of vowels in each substring of length K. Also, we can use the sliding window approach to solve the problem. Problem statement – We have given a string str of length N containing lowercase and uppercase alphabetical characters. We need to count the total number of substrings of length K which contains exactly X vowels. Sample examples Input– str = ... Read More

In this problem, we need th check whether the substring S1 appears after any occurrence of the substring S2 in the given string S. We can compare the starting index of S1 and S2 in the string S to solve the problem. Problem statement – We have given three substrings named S, S1, and S2. The string S always contains S1 as a substring. We need to check whether the substring S1 appears after any occurrence of the substring S2 in the given string S. Sample examples Input – S = "abxtutorialspointwelcomepoint", S1 = "welcome", S2 = "point"; ... Read More

We have given two strings and need to check whether the given string's permutations exist such that one permutation can have a larger character than another permutation at the ith index. We can solve the problem by sorting the string and comparing each character of the string one by one. Also, we can solve the problem using the frequency of characters of both strings. Problem statement – We have given a string str1 and str2 of length N. We need to check whether any permutations of both strings exist such that the permutation of one string is lexicographically larger than ... Read More

In this problem, we need to find the maximum length of the sub sequence with the same left and right rotations. The left rotation means moving all characters of the string in the left direction and the first character at the end. The right rotation means moving all string characters in the right direction and the last character at the start. Problem statement – We have given string str containing numeric digits and need to find the sub sequence of maximum length with the same left and right rotations. Sample examples Input – str = "323232", Output – 6 Explanation– ... Read More

In this problem, we need to find the average value of the count of set bits after performing K operations of all choices on the given string. There can be a brute force approach to solve the problem, but we will use the probability principles to overcome the time complexity of the brute force approach. Problem statement – We have given an integer N, array arr[] containing K positive integers, and a binary string of length N containing only set bits. We need to find the average value of the count of set bits after performing all possible choices ... Read More

In this problem, we need to find the total number of sub strings of length K containing at most X distinct vowels. We can solve the problem in two different ways. The first way is to get all sub strings and count distinct vowels in each sub string of length K. The second way is to use a map data structure and track the number of distinct vowels in the particular sub string. Problem statement– We have given string str of length N. The string contains only alphabetical characters. Also, we have given K and X positive integers. We need ... Read More