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65
leetcode_java/src/main/java/LeetCodeJava/String/ValidPalindrome.java
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| @@ -0,0 +1,65 @@ | ||
| package LeetCodeJava.String; | ||
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| // https://leetcode.com/problems/valid-palindrome/description/?envType=list&envId=xoqag3yj | ||
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| /** | ||
| * 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 letters and numbers. | ||
| * | ||
| * | ||
| * NOTE !!! | ||
| * | ||
| * "and removing all non-alphanumeric characters, " | ||
| * -> so we need to consider both alphabet and numeric element | ||
| */ | ||
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| public class ValidPalindrome { | ||
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| // V0 | ||
| public boolean isPalindrome(String s) { | ||
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| if (s == null || s.length() == 0){ | ||
| return true; | ||
| } | ||
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| String sUpper = ""; | ||
| for (int idx = 0; idx < s.length(); idx++){ | ||
| if (Character.isLetterOrDigit(s.charAt(idx))){ | ||
| sUpper += String.valueOf(s.charAt(idx)).toUpperCase(); | ||
| } | ||
| } | ||
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| //System.out.println("sUpper = " + sUpper); | ||
| //String sUpper = s.toUpperCase(); | ||
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| // 2 pointer | ||
| int l = 0; | ||
| int r = sUpper.length() - 1; | ||
| while (r > l){ | ||
| if (sUpper.charAt(l) != sUpper.charAt(r)){ | ||
| return false; | ||
| } | ||
| l += 1; | ||
| r -= 1; | ||
| } | ||
| return true; | ||
| } | ||
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| // V1 | ||
| // https://leetcode.com/problems/valid-palindrome/solutions/4787889/simple-solution-using-java/?envType=list&envId=xoqag3yj | ||
| public boolean isPalindrome_1(String s) { | ||
| String str=s.replaceAll("[^a-zA-Z0-9]","").toLowerCase(); | ||
| StringBuilder sb=new StringBuilder(str); | ||
| sb.reverse(); | ||
| String ans=sb.toString(); | ||
| for(int i=0;i<str.length();i++){ | ||
| if(str.charAt(i)!=ans.charAt(i)){ | ||
| return false; | ||
| } | ||
| } | ||
| return true; | ||
| } | ||
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| } |