Time: 39 ms (36.42%), Space: 16.5 MB (67.95%) - LeetHub

Author: hogan-tech

0564-find-the-closest-palindrome/0564-find-the-closest-palindrome.py

@@ -0,0 +1,45 @@
+# time complexity: O(n)
+# space complexity: O(n)
+class Solution:
+    def nearestPalindromic(self, n: str) -> str:
+        lenN = len(n)
+        i = lenN // 2 - 1 if lenN % 2 == 0 else lenN // 2
+        firstHalf = int(n[: i + 1])
+        possibilities = []
+        possibilities.append(
+            self.halfToPalindrome(firstHalf, lenN % 2 == 0)
+        )
+        possibilities.append(
+            self.halfToPalindrome(firstHalf + 1, lenN % 2 == 0)
+        )
+        possibilities.append(
+            self.halfToPalindrome(firstHalf - 1, lenN % 2 == 0)
+        )
+        possibilities.append(10 ** (lenN - 1) - 1)
+        possibilities.append(10**lenN + 1)
+
+        diff = float("inf")
+        res = 0
+        nl = int(n)
+        for cand in possibilities:
+            if cand == nl:
+                continue
+            if abs(cand - nl) < diff:
+                diff = abs(cand - nl)
+                res = cand
+            elif abs(cand - nl) == diff:
+                res = min(res, cand)
+        return str(res)
+
+    def halfToPalindrome(self, left: int, even: bool) -> int:
+        res = left
+        if not even:
+            left = left // 10
+        while left > 0:
+            res = res * 10 + left % 10
+            left //= 10
+        return res
+
+
+n = "123"
+print(Solution().nearestPalindromic(n))