What is a Palindrome String?

A string is called a palindrome if the reverse of the string is the same as the original one.

Example: “madam”, “racecar”, “12321”.

Palindrome String

Properties of a Palindrome:

A palindrome string has some properties which are mentioned below:

• A palindrome string has a symmetric structure which means that the character in the first half of the string are the same as in the rear half but in reverse order.
• Any string of length 1 is always a palindrome.

How to identify a Palindrome?

We can follow the below steps to identify a palindrome:

• Depending on the case sensitivity, either turn all the characters to lowercase or uppercase or keep them as it is.
• Now, Compare the first and the last character. If they are the same move to the second and second last and so on.
• If all the pairs of characters match, then it is a palindrome, otherwise not.

Easy Problems on Palindrome:

• C Program to Check if a Given String is Palindrome
• Recursive function to check if a string is palindrome
• Sentence Palindrome (Palindrome after removing spaces, dots, .. etc)
• Check if actual binary representation of a number is palindrome
• Print longest palindrome word in a sentence
• Count palindrome words in a sentence
• Check if characters of a given string can be rearranged to form a palindrome
• Lexicographically first palindromic string
• Longest Non-palindromic substring
• Minimum insertions to form a palindrome with permutations allowed
• Smallest Palindrome after replacement
• Remove a character from a string to make it a palindrome
• Program to print all palindromes in a given range
• Sum of first K even-length Palindrome numbers

Medium Problems on Palindrome:

• Minimum removal to make palindrome permutation
• Print the arranged positions of characters to make palindrome
• Check if a given string is a rotation of a palindrome
• Make largest palindrome by changing at most K-digits
• Minimum number of deletions to make a string palindrome
• Find longest palindrome formed by removing or shuffling chars from string
• Print all palindrome permutations of a string
• Find all palindromic sub-strings of a given string
• Count of Palindromic substrings in an Index range
• Longest Possible Chunked Palindrome
• Largest palindromic number by permuting digits
• Make a lexicographically smallest palindrome with minimal changes
• Number of strings of length N with no palindromic sub string
• Check if any anagram of a string is palindrome or not
• Count maximum-length palindromes in a String
• Next higher palindromic number using the same set of digits

Hard Problems on Palindrome:

• Minimum insertions to form a palindrome | DP-28
• Longest Palindromic Substring
• Online algorithm for checking palindrome in a stream
• Palindrome Partitioning | DP-17
• Print all palindromic partitions of a string
• Count All Palindromic Subsequence in a given String
• Print Longest Palindromic Subsequence
• Minimum characters to be added at front to make string palindrome
• Palindrome Substring Queries
• Palindrome pair in an array of words (or strings)
• Minimum steps to delete a string after repeated deletion of palindrome substrings
• Given a number, find the next smallest palindrome
• Closest Palindrome Number (absolute difference Is min)
• Count palindromic characteristics of a String
• Number of positions where a letter can be inserted such that a string becomes palindrome
• Minimum equal palindromic cuts with rearrangements allowed
• Palindrome by swapping only one character

Quick Links:

• Recent articles on Palindrome
• ‘Practice Problems’ on Strings
• ‘Quizzes’ on Strings