Added Longest Palindromic SubString

Ace-Krypton · Sep 3, 2023 · 5c5dd77 · 5c5dd77
1 parent b33002b
commit 5c5dd77
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Showing 2 changed files with 33 additions and 2 deletions.
diff --git a/Medium/LongestPalindromicSubstring/include/solution.hpp b/Medium/LongestPalindromicSubstring/include/solution.hpp
@@ -7,7 +7,7 @@
 
 class Solution {
 public:
-    static auto longest_palindrome(const std::string &s) -> std::string {
+    [[maybe_unused]] static auto longest_palindrome_tle(const std::string &s) -> std::string {
         std::string ans;
         std::size_t max_length = 0;
 
@@ -27,4 +27,35 @@ class Solution {
 
         return ans;
     }
+
+    static auto longest_palindrome(const std::string &s) -> std::string {
+        if (s.empty()) return { };
+
+        int32_t start = 0;
+        int32_t end = 0;
+
+        for (int32_t i = 0; i < s.length(); ++i) {
+            int32_t len1 = expand_around_center(s, i, i);
+            int32_t len2 = expand_around_center(s, i, i + 1);
+
+            int32_t len = std::max(len1, len2);
+
+            if (len > end - start) {
+                start = i - (len - 1) / 2;
+                end = i + len / 2;
+            }
+        }
+
+        return s.substr(start, end - start + 1);
+    }
+
+    static auto expand_around_center(const std::string &s,
+                                     int32_t left, int32_t right) -> int32_t {
+        while (left >= 0 && right < s.length()
+            && s[left] == s[right]) {
+            left--;
+            right++;
+        }
+        return right - left - 1;
+    }
 };
diff --git a/Medium/LongestPalindromicSubstring/tests/test.cpp b/Medium/LongestPalindromicSubstring/tests/test.cpp
@@ -9,7 +9,7 @@ TEST_F(LongestPalindromicSubstring, FirstTest) {
     std::string element = "babad";
 
     std::string result = Solution::longest_palindrome(element);
-    std::string expected = "bab";
+    std::string expected = "aba";
 
     ASSERT_EQ(result, expected);
 }