# Longest Non-palindromic substring

Given a string of size n. The task is to find the length of the largest substring which is not 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
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

A simple solution is to consider every substring and check if it is palindrome or not. Finally return length of the longest non-palindromic substring.

An efficient solution is based on 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' ```

## 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

```//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
```

Output:

```Maximum length = 3
```

Time Complexity: O(n)

This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

# GATE CS Corner    Company Wise Coding Practice

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.
1.8 Average Difficulty : 1.8/5.0
Based on 10 vote(s)

Writing code in comment? Please use ide.geeksforgeeks.org, generate link and share the link here.