# Longest palindrome in a given string using LINQ

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Problem

Problem:I need to write an algorithm that will return length of longest possible palindrome from a given string.

So if the input is aabbbccdfg
Program output should be 7. //–>[cabbbac]

Can someone point it out if there are any problems with below code?

``````public static void GetLongestPalindromeLength()
{
var result = 0;
var countsByChar = input.GroupBy(c => c);
var oddCounts = countsByChar.Where(g => g.Count() % 2 != 0).Select(g => g.Count()).ToList();
var evenCounts = countsByChar.Where(g => g.Count() % 2 == 0).Select(g => g.Count()).ToList();
if (oddCounts.Any())
{
var max = oddCounts.Max();
result += max;
oddCounts.RemoveAt(oddCounts.FindIndex(e => e == max));
result += evenCounts.Sum();
result += oddCounts.Sum(e => e - 1);
}
else if (evenCounts.Any())
{
result += evenCounts.Sum();
}
Console.WriteLine(result);
}
``````

Solution

Well, I think your algorithm is correct, but the code is quite bloat. Your code suggest that the longest palindrome size can be calculated by sum of `n / 2 * 2` where `n` is the count of distinct alphabet that exists more than once in the string, and plus 1 if there are any “oddCounts”. So you can reduce the code to

``````    private static int GetLongestPalindrome(string value) {
var map = value.GroupBy(c => c);
int result = map.Sum(r => r.Count() / 2 * 2);
if (map.Any(r => r.Count() % 2 != 0))
{
result++;
}
return result;
}
``````

`n / 2 * 2` is the way to calculate for the nearest even number toward zero, and it equals to `n - 1` where `n` is positive odd number.