Longest Non-palindromic substring
Last Updated : 11 Jul, 2022
Given a string of size n. The task is to find the length of the largest substring which is not a palindrome.
Examples:
Input : abba Output : 3 Here maximum length non-palindromic substring is 'abb' which is of length '3'. There could be other non-palindromic sub-strings also of length three like 'bba' in this case. Input : a Output : 0
A simple solution is to consider every substring and check if it is palindrome or not. Finally, return the length of the longest non-palindromic substring.
An efficient solution is based on the below approach.
Check for the case where all characters of the string are same or not. If yes, then answer will be '0'. Else check whether the given string of size 'n' is palindrome or not. If yes, then answer will be 'n-1' Else answer will be 'n'
Implementation:
C++ // C++ implementation to find maximum length // substring which is not palindrome #include <bits/stdc++.h> using namespace std; // utility function to check whether // a string is palindrome or not bool isPalindrome(string str) { // Check for palindrome. int n = str.size(); for (int i=0; i < n/2; i++) if (str.at(i) != str.at(n-i-1)) return false; // palindrome string return true; } // function to find maximum length // substring which is not palindrome int maxLengthNonPalinSubstring(string str) { int n = str.size(); char ch = str.at(0); // to check whether all characters // of the string are same or not int i = 1; for (i=1; i<n; i++) if (str.at(i) != ch) break; // All characters are same, we can't // make a non-palindromic string. if (i == n) return 0; // If string is palindrome, we can make // it non-palindrome by removing any // corner character if (isPalindrome(str)) return n-1; // Complete string is not a palindrome. return n; } // Driver program to test above int main() { string str = "abba"; cout << "Maximum length = " << maxLengthNonPalinSubstring(str); return 0; } //Java implementation to find maximum length //substring which is not palindrome public class GFG { // utility function to check whether // a string is palindrome or not static Boolean isPalindrome(String str) { int n = str.length(); // Check for palindrome. for (int i = 0; i < n/2; i++) if (str.charAt(i) != str.charAt(n-i-1)) return false; // palindrome string return true; } // function to find maximum length // substring which is not palindrome static int maxLengthNonPalinSubstring(String str) { int n = str.length(); char ch = str.charAt(0); // to check whether all characters // of the string are same or not int i = 1; for (i = 1; i < n; i++) if(str.charAt(i) != ch) break; // All characters are same, we can't // make a non-palindromic string. if (i == n) return 0; // If string is palindrome, we can make // it non-palindrome by removing any // corner character if (isPalindrome(str)) return n-1; // Complete string is not a palindrome. return n; } // Driver Program to test above function public static void main(String args[]) { String str = "abba"; System.out.println("Maximum Length = " + maxLengthNonPalinSubstring(str)); } } // This code is contributed by Sumit Ghosh # Python 3 implementation to find maximum # length substring which is not palindrome # utility function to check whether # a string is palindrome or not def isPalindrome(str): # Check for palindrome. n = len(str) for i in range(n // 2): if (str[i] != str[n - i - 1]): return False # palindrome string return True # function to find maximum length # substring which is not palindrome def maxLengthNonPalinSubstring(str): n = len(str) ch = str[0] # to check whether all characters # of the string are same or not i = 1 for i in range(1, n): if (str[i] != ch): break # All characters are same, we can't # make a non-palindromic string. if (i == n): return 0 # If string is palindrome, we can make # it non-palindrome by removing any # corner character if (isPalindrome(str)): return n - 1 # Complete string is not a palindrome. return n # Driver Code if __name__ == "__main__": str = "abba" print("Maximum length =", maxLengthNonPalinSubstring(str)) # This code is contributed by ita_c // C# implementation to find maximum length // substring which is not palindrome using System; class GFG { // utility function to check whether // a string is palindrome or not static bool isPalindrome(String str) { int n = str.Length; // Check for palindrome. for (int i = 0; i < n / 2; i++) if (str[i] != str[n - i - 1]) return false; // palindrome string return true; } // function to find maximum length // substring which is not palindrome static int maxLengthNonPalinSubstring(String str) { int n = str.Length; char ch = str[0]; // to check whether all characters // of the string are same or not int i = 1; for (i = 1; i < n; i++) if(str[i] != ch) break; // All characters are same, we can't // make a non-palindromic string. if (i == n) return 0; // If string is palindrome, we can // make it non-palindrome by removing // any corner character if (isPalindrome(str)) return n-1; // Complete string is not a palindrome. return n; } // Driver code public static void Main() { String str = "abba"; Console.Write("Maximum Length = " + maxLengthNonPalinSubstring(str)); } } // This code is contributed by nitin mittal <?php // PHP implementation to find maximum length // substring which is not palindrome // utility function to check whether // a string is palindrome or not function isPalindrome($str) { $n = strlen($str); // Check for palindrome. for ($i = 0; $i < $n / 2; $i++) if ($str[$i] != $str[$n - $i - 1]) return false; // palindrome string return true; } // function to find maximum length // substring which is not palindrome function maxLengthNonPalinSubstring($str) { $n = strlen($str); $ch = $str[0]; // to check whether all characters // of the string are same or not $i = 1; for ($i = 1; $i < $n; $i++) if($str[$i] != $ch) break; // All characters are same, we can't // make a non-palindromic string. if ($i == $n) return 0; // If string is palindrome, we can // make it non-palindrome by removing // any corner character if (isPalindrome($str)) return ($n - 1); // Complete string is not a palindrome. return $n; } // Driver code $str = "abba"; echo "Maximum Length = ", maxLengthNonPalinSubstring($str); // This code is contributed by ajit ?> <script> //Javascript implementation to find maximum length //substring which is not palindrome // utility function to check whether // a string is palindrome or not function isPalindrome(str) { let n=str.length; // Check for palindrome. for (let i = 0; i < n/2; i++) { if(str[i] != str[n-i-1]) return false; } // palindrome string return true; } // function to find maximum length // substring which is not palindrome function maxLengthNonPalinSubstring(str) { let n = str.length; let ch=str[0]; // to check whether all characters // of the string are same or not let i = 1; for (i = 1; i < n; i++) { if(str[i] != ch) { break; } } // All characters are same, we can't // make a non-palindromic string. if (i == n) return 0; // If string is palindrome, we can make // it non-palindrome by removing any // corner character if (isPalindrome(str)) return n-1; // Complete string is not a palindrome. return n; } // Driver Program to test above function let str = "abba"; document.write("Maximum Length = " + maxLengthNonPalinSubstring(str)); // This code is contributed by avanitrachhadiya2155 </script> Time Complexity: O(n)
Auxiliary Space: O(n)
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