String | Palindrome

What is a Palindrome String?

A string is called a palindrome if the reverse of the string is the same as the original one. For example, “madam”, “racecar”, “12321”.

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.

Some practice problems on Palindrome:

• Easy:
  1. C Program to Check if a Given String is Palindrome
  2. Recursive function to check if a string is palindrome
  3. Sentence Palindrome (Palindrome after removing spaces, dots, .. etc)
  4. Check if actual binary representation of a number is palindrome
  5. Print longest palindrome word in a sentence
  6. Count palindrome words in a sentence
  7. Check if characters of a given string can be rearranged to form a palindrome
  8. Lexicographically first palindromic string
  9. Longest Non-palindromic substring
  10. Minimum insertions to form a palindrome with permutations allowed
  11. Smallest Palindrome after replacement
  12. Remove a character from a string to make it a palindrome
  13. Program to print all palindromes in a given range
  14. Sum of first K even-length Palindrome numbers
• Intermediate:
  1. Minimum removal to make palindrome permutation
  2. Print the arranged positions of characters to make palindrome
  3. Check if a given string is a rotation of a palindrome
  4. Make largest palindrome by changing at most K-digits
  5. Minimum number of deletions to make a string palindrome
  6. Find longest palindrome formed by removing or shuffling chars from string
  7. Print all palindrome permutations of a string
  8. Find all palindromic sub-strings of a given string
  9. Count of Palindromic substrings in an Index range
  10. Longest Possible Chunked Palindrome
  11. Largest palindromic number by permuting digits
  12. Make a lexicographically smallest palindrome with minimal changes
  13. Number of strings of length N with no palindromic sub string
  14. Check if any anagram of a string is palindrome or not
  15. Count maximum-length palindromes in a String
  16. Next higher palindromic number using the same set of digits
• Hard:
  1. Minimum insertions to form a palindrome | DP-28
  2. Longest Palindromic Substring
  3. Online algorithm for checking palindrome in a stream
  4. Palindrome Partitioning | DP-17
  5. Print all palindromic partitions of a string
  6. Count All Palindromic Subsequence in a given String
  7. Print Longest Palindromic Subsequence
  8. Minimum characters to be added at front to make string palindrome
  9. Palindrome Substring Queries
  10. Palindrome pair in an array of words (or strings)
  11. Minimum steps to delete a string after repeated deletion of palindrome substrings
  12. Given a number, find the next smallest palindrome
  13. Closest Palindrome Number (absolute difference Is min)
  14. Count palindromic characteristics of a String
  15. Number of positions where a letter can be inserted such that a string becomes palindrome
  16. Minimum equal palindromic cuts with rearrangements allowed
  17. Palindrome by swapping only one character

Quick Links:

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