Add LongestPalindromicSubstring in C# (TheRenegadeCoder#3989)

rifflere · Nov 8, 2024 · 4ce60e7 · 4ce60e7
1 parent 7c09559
commit 4ce60e7
Showing 1 changed file with 71 additions and 0 deletions.
diff --git a/archive/c/c-sharp/LongestPalindromicSubstring.cs b/archive/c/c-sharp/LongestPalindromicSubstring.cs
@@ -0,0 +1,71 @@
+using System;
+using System.Text.RegularExpressions;
+
+namespace SamplePrograms
+{
+    public class LongestPalindromicSubstring
+    {
+        public static void Main(string[] args)
+        {
+            string input = string.Join(" ", args);
+            Console.WriteLine(LongestPalindrome(input));
+        }
+
+        public static string LongestPalindrome(string input)
+        {
+            if (string.IsNullOrEmpty(input) || !ContainsPalindrome(input))
+            {
+                return "Usage: please provide a string that contains at least one palindrome";
+            }
+
+            int start = 0;
+            int end = 0;
+
+            for (int i = 0; i < input.Length; i++)
+            {
+                int lengthOne = ExpandAroundCenter(input, i, i);
+                int lengthTwo = ExpandAroundCenter(input, i, i + 1);
+                int length = Math.Max(lengthOne, lengthTwo);
+
+                if (length > end - start)
+                {
+                    start = i - (length - 1) / 2;
+                    end = i + length / 2;
+                }
+            }
+            return input.Substring(start, end - start + 1);
+        }
+
+        private static int ExpandAroundCenter(string input, int left, int right)
+        {
+            while (left >= 0 && right < input.Length && input[left] == input[right])
+            {
+                left--;
+                right++;
+            }
+            return right - left - 1;
+        }
+
+        private static bool ContainsPalindrome(string input)
+        {
+            string[] words = input.Split(' ');
+            foreach (string word in words)
+            {
+                if (word.Length > 1 && word == Reverse(word))
+                {
+                    return true;
+                }
+            }
+
+            string cleanedInput = input.Replace(" ", "");
+            return cleanedInput.Length > 1 && cleanedInput == Reverse(cleanedInput);
+        }
+
+        private static string Reverse(string input)
+        {
+            char[] charArray = input.ToCharArray();
+            Array.Reverse(charArray);
+            return new string(charArray);
+        }
+    }
+}