leetcode

commit a1bd06c84b438b48a6c01fb1b14d74571752cf50
parent d9f08bf1f55bbdd365c8204ad5261a66f7d8fc25
Author: Jack Sangdahl <jack@pngu.org>
Date:   Thu, 27 Feb 2025 12:00:57 -0700

125. valid palindrome

Diffstat:
A
valid_palindrome.c
 | 
35
+++++++++++++++++++++++++++++++++++
A
valid_palindrome.py
 | 
35
+++++++++++++++++++++++++++++++++++

2 files changed, 70 insertions(+), 0 deletions(-)
diff --git a/valid_palindrome.c b/valid_palindrome.c
@@ -0,0 +1,35 @@
+// 125. Valid Palindrome
+#include "leetcode.h"
+
+/*
+ * a phrase is a palindrome if, after converting all uppercase letters into
+ * lowercase letters, and removing all non-alphanumeric characters, it reads the
+ * same forward and backward. alphanumeric characters include only letters and
+ * numbers. given a string 's', return true if it is a palindrome, or false
+ * otherwise.
+ */
+
+bool isPalindrome(char *s) {
+  int l = 0, r = strlen(s) - 1;
+  while (l < r) {
+    if (isalnum(s[l])) {
+      if (isalnum(s[r])) {
+        if (tolower(s[l]) != tolower(s[r]))
+          return false;
+        l++, r--;
+      } else
+        r--;
+    } else
+      l++;
+  }
+  return true;
+}
+
+int main() {
+  char *s1 = "A man, a plan, a canal: Panama";
+  char *s2 = "race a car";
+  char *s3 = " ";
+  printf("%d\n", isPalindrome(s1)); // expect: 1
+  printf("%d\n", isPalindrome(s2)); // expect: 0
+  printf("%d\n", isPalindrome(s3)); // expect: 1
+}
diff --git a/valid_palindrome.py b/valid_palindrome.py
@@ -0,0 +1,35 @@
+# 125. Valid Palindrome
+
+"""
+a phrase is a palindrome if, after converting all uppercase letters into
+lowercase letters, and removing all non-alphanumeric characters, it reads the
+same forward and backward. alphanumeric characters include only letters and
+numbers. given a string 's', return true if it is a palindrome, or false
+otherwise.
+"""
+
+
+class Solution(object):
+    def isPalindrome(self, s):
+        """
+        :type s: str
+        :rtype: bool
+        """
+        l, r = 0, len(s) - 1
+        while l < r:
+            while l < r and not s[l].isalnum():
+                l += 1
+            while l < r and not s[r].isalnum():
+                r -= 1
+            if s[l].lower() != s[r].lower():
+                return False
+            l += 1
+            r -= 1
+        return True
+
+
+if __name__ == "__main__":
+    obj = Solution()
+    print(obj.isPalindrome(s="A man, a plan, a canal: Panama"))
+    print(obj.isPalindrome(s="race a car"))
+    print(obj.isPalindrome(s=" "))