Q:

Write a C# Sharp program to get the longest Palindromic substring from a given string

hamza
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2022-05-18
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Write a C# Sharp program to get the longest Palindromic substring from a given string. 

From Wikipedia:
In computer science, the longest palindromic substring or longest symmetric factor problem is the problem of finding a maximum-length contiguous substring of a given string that is also a palindrome. For example, the longest palindromic substring of "bananas" is "anana". The longest palindromic substring is not guaranteed to be unique; for example, in the string "abracadabra", there is no palindromic substring with length greater than three, but there are two palindromic substrings with length three, namely, "aca" and "ada".

Expected Output :

Original String: aaaaaabbbbccc
Length of the longest substring without repeating characters of the said string:
aaaaa
Original String: BDEFGAABEF
Length of the longest substring without repeating characters of the said string:
AA
Original String: Python
Length of the longest substring without repeating characters of the said string:
P
Original String: Java
Length of the longest substring without repeating characters of the said string:
av
c# programming, Programming,
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All Answers

hamza
2022-05-18
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using System;
using System.Collections.Generic;
namespace exercises {
  class Program {
    static void Main(string[] args) {
      String str1;
      str1 = "aaaaaabbbbccc";
      Console.WriteLine("Original String: " + str1);
      Console.WriteLine("Length of the longest substring without repeating characters of the said string:");
      Console.WriteLine(longest_Palindrome(str1));
      str1 = "BDEFGAABEF";
      Console.WriteLine("Original String: " + str1);
      Console.WriteLine("Length of the longest substring without repeating characters of the said string:");;
      Console.WriteLine(longest_Palindrome(str1));
      str1 = "Python";
      Console.WriteLine("Original String: " + str1);
      Console.WriteLine("Length of the longest substring without repeating characters of the said string:");
      Console.WriteLine(longest_Palindrome(str1));
      str1 = "Java";
      Console.WriteLine("Original String: " + str1);
      Console.WriteLine("Length of the longest substring without repeating characters of the said string:");
      Console.WriteLine(longest_Palindrome(str1));
    }
    public static string longest_Palindrome(string s) {
      var chars_array = s.ToCharArray();
      var bool_arr = new bool[chars_array.Length, chars_array.Length];
      int longest_start = 0;
      int max_length = 1;
      for (int i = 0; i < chars_array.Length; i++) {
        bool_arr[i, i] = true;
      }
      for (int i = 0; i < chars_array.Length - 1; i++) {
        if (chars_array[i] == chars_array[i + 1]) {
          bool_arr[i, i + 1] = true;
          longest_start = i;
          max_length = 2;
        }
      }
      for (int length = 3; length <= chars_array.Length; length++) {
        for (int i = 0; i < chars_array.Length - length + 1; i++) {
          int j = i + length - 1;
          if (chars_array[i] == chars_array[j] && bool_arr[i + 1, j - 1]) {
            bool_arr[i, j] = true;
            if (max_length < (j - i)) {
              max_length = j - i;
              longest_start = i;
            }
          }
        }
      }
      return s.Substring(longest_start, max_length);
    }
  }
}

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