Blind 75
Valid Palindrome
- Problem
- LC 125
- Category
- String
- File
- blind75_LC125ValidPalindrome.java
- Path
- pkg5leetcode/blind75/blind75_LC125ValidPalindrome.java
- Package
- pkg5leetcode.blind75
- Command
- java pkg5leetcode/blind75/blind75_LC125ValidPalindrome.java
- Approach
- Two pointers skip non-alphanumeric, compare lowercased.
- Complexity
- Time O(n), Space O(1)
There is no in-browser runner. This is the file from the curriculum, unchanged.
1package pkg5leetcode.blind75;2 3/*4 * Valid Palindrome | LC 1255 * APPROACH: Two pointers skip non-alphanumeric, compare lowercased.6 * COMPLEXITY: Time O(n), Space O(1)7 */8public class blind75_LC125ValidPalindrome {9 static boolean isPalindrome(String s) {10 int lo = 0, hi = s.length() - 1;11 while (lo < hi) {12 while (lo < hi && !Character.isLetterOrDigit(s.charAt(lo))) lo++;13 while (lo < hi && !Character.isLetterOrDigit(s.charAt(hi))) hi--;14 if (Character.toLowerCase(s.charAt(lo)) != Character.toLowerCase(s.charAt(hi))) return false;15 lo++; hi--;16 }17 return true;18 }19 20 public static void main(String[] args) {21 check(isPalindrome("A man, a plan, a canal: Panama"), "case1");22 check(!isPalindrome("race a car"), "case2");23 System.out.println("all tests passed");24 }25 26 static void check(boolean cond, String name) {27 if (!cond) throw new AssertionError("FAILED: " + name);28 System.out.println(" PASS " + name);29 }30}