Add Shortest Palindrome

Author: thanthtooaung-coding

README.md

@@ -17,14 +17,15 @@ Each problem has its own directory containing:
 | 3 | [Longest Substring Without Repeating Characters](Longest%20Substring%20Without%20Repeating%20Characters) | Medium | [Java](Longest%20Substring%20Without%20Repeating%20Characters/Solution.java) | Hash Table, String, Sliding Window |
 | 4 | [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays) | Hard | [Java](Median%20of%20Two%20Sorted%20Arrays/Solution.java) | Array, Binary Search, Divide and Conquer |
 | 5 | [Longest Palindromic Substring](Longest%20Palindromic%20Substring) | Medium | [Java](Longest%20Palindromic%20Substring/Solution.java) | Two Pointers, String, Dynamic Programming |
+| 214 | [Shortest Palindrome](Shortest%20Palindrome) | Hard | [Java](Shortest%20Palindrome/Solution.java) | String, Rolling Hash, String Matching, Hash Function |
 | 2924 | [Find Champion II](Find%20Champion%20II) | Medium | [Java](Find%20Champion%20II/Solution.java) | Graph |
 
 ## Categories
 
 ### By Difficulty
 - Easy: 1
 - Medium: 4
-- Hard: 1
+- Hard: 2
 
 ### By Topics
 - Array Problems
@@ -36,6 +37,7 @@ Each problem has its own directory containing:
 - String Problems
   - [Longest Substring Without Repeating Characters](Longest%20Substring%20Without%20Repeating%20Characters)
   - [Longest Palindromic Substring](Longest%20Palindromic%20Substring)
+  - [Shortest Palindrome](Shortest%20Palindrome)
 - Dynamic Programming Problems
   - [Longest Palindromic Substring](Longest%20Palindromic%20Substring)
 - Linked List Problems
@@ -46,6 +48,8 @@ Each problem has its own directory containing:
   - [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays)
 - Graph Problems
   - [Find Champion II](Find%20Champion%20II)
+- String Matching Problems
+  - [Shortest Palindrome](Shortest%20Palindrome)
 
 ## About LeetCode
 

Shortest Palindrome/README.md

@@ -0,0 +1,34 @@
+# Shortest Palindrome
+
+## LeetCode Problem
+- Problem Number: 214
+- Problem Link: https://leetcode.com/problems/shortest-palindrome/
+- Difficulty: Hard
+- Topics: String, Rolling Hash, String Matching, Hash Function
+
+## Problem Description
+Given a string s, you can convert it to a palindrome by adding characters in front of it.
+
+Return the shortest palindrome you can find by performing this transformation.
+
+Note:
+- A palindrome is a string that reads the same forward and backward
+- You can only add characters to the front of the string
+
+## Examples
+
+### Example 1:
+```
+Input: s = "aacecaaa"
+Output: "aaacecaaa"
+```
+
+### Example 2:
+```
+Input: s = "abcd"
+Output: "dcbabcd"
+```
+
+## Constraints
+- 0 <= s.length <= 5 * 10⁴
+- s consists of lowercase English letters only

Shortest Palindrome/Solution.java

@@ -0,0 +1,43 @@
+class Solution {
+    public String shortestPalindrome(String s) {
+        if (s == null || s.length() <= 1) {
+            return s;
+        }
+        
+        String reversed = new StringBuilder(s).reverse().toString();
+        String combined = s + "#" + reversed;
+        
+        int[] lps = computeLPS(combined);
+        
+        int longestPrefix = lps[lps.length - 1];
+        
+        String suffix = s.substring(longestPrefix);
+        String prefix = new StringBuilder(suffix).reverse().toString();
+        
+        return prefix + s;
+    }
+    
+    private int[] computeLPS(String s) {
+        int n = s.length();
+        int[] lps = new int[n];
+        int length = 0;
+        int i = 1;
+        
+        while (i < n) {
+            if (s.charAt(i) == s.charAt(length)) {
+                length++;
+                lps[i] = length;
+                i++;
+            } else {
+                if (length > 0) {
+                    length = lps[length - 1];
+                } else {
+                    lps[i] = 0;
+                    i++;
+                }
+            }
+        }
+        
+        return lps;
+    }
+}