adding algo

src/my_project/interviews/top_150_questions_round_22/ex_140_longest_palindromic_substring.py

@@ -0,0 +1,19 @@
+class Solution:
+    def longestPalindrome(self, s: str) -> str:
+        start, max_len = 0, 1
+
+        def expand(left: int, right: int) -> None:
+            nonlocal start, max_len
+            while left >= 0 and right < len(s) and s[left] == s[right]:
+                left -= 1
+                right += 1
+            length = right - left - 1
+            if length > max_len:
+                max_len = length
+                start = left + 1
+
+        for i in range(len(s)):
+            expand(i, i)      # odd-length
+            expand(i, i + 1)  # even-length
+
+        return s[start:start + max_len]

src/my_project/interviews_typescript/top_150_questions_round_1/ex_140_longest_palindromic_substring.ts

@@ -0,0 +1,22 @@
+function longestPalindrome(s: string): string {
+    let start = 0, maxLen = 1;
+
+    const expand = (left: number, right: number): void => {
+        while (left >= 0 && right < s.length && s[left] === s[right]) {
+            left--;
+            right++;
+        }
+        const length = right - left - 1;
+        if (length > maxLen) {
+            maxLen = length;
+            start = left + 1;
+        }
+    };
+
+    for (let i = 0; i < s.length; i++) {
+        expand(i, i);       // odd-length
+        expand(i, i + 1);   // even-length
+    }
+
+    return s.substring(start, start + maxLen);
+}

tests/test_150_questions_round_22/test_140_longest_palindromic_substring_round_22.py

@@ -0,0 +1,35 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_22\
+.ex_140_longest_palindromic_substring import Solution
+
+
+class LongestPalindromicSubstringTestCase(unittest.TestCase):
+    def setUp(self):
+        self.solution = Solution()
+
+    def test_example_1(self):
+        result = self.solution.longestPalindrome("babad")
+        self.assertIn(result, ("bab", "aba"))
+
+    def test_example_2(self):
+        self.assertEqual("bb", self.solution.longestPalindrome("cbbd"))
+
+    def test_single_char(self):
+        self.assertEqual("a", self.solution.longestPalindrome("a"))
+
+    def test_all_same(self):
+        self.assertEqual("aaaa", self.solution.longestPalindrome("aaaa"))
+
+    def test_no_palindrome_longer_than_one(self):
+        result = self.solution.longestPalindrome("abcd")
+        self.assertEqual(1, len(result))
+
+    def test_even_palindrome(self):
+        self.assertEqual("abba", self.solution.longestPalindrome("cabba"))
+
+    def test_full_string_palindrome(self):
+        self.assertEqual("racecar", self.solution.longestPalindrome("racecar"))
+
+
+if __name__ == '__main__':
+    unittest.main()