Update 125-Valid-Palindrome.js

javascript/125-Valid-Palindrome.js

@@ -1,54 +1,77 @@
 /**
+ * Array - Filter && Clone && Reverse
+ * Time O(N) | Space O(N)
  * https://leetcode.com/problems/valid-palindrome/
- * Time O(N^2) | Space O(1)
  * @param {string} s
  * @return {boolean}
  */
-var isPalindrome = function (s) {
+var isPalindrome = function(s) {
  if (!s.length) return true;
+
+ const alphaNumeric = filterAlphaNumeric(s);/* Time O(N) | Space O(N) */
+ const reversed = reverse(alphaNumeric); /* Time O(N) | Space O(N) */
+
+ return alphaNumeric === reversed;
+};
+
+const filterAlphaNumeric = (s, nonAlphaNumeric = new RegExp('[^a-z0-9]','gi')) => s
+ .toLowerCase() /* Time O(N) | Space O(N) */
+ .replace(nonAlphaNumeric, '')/* Time O(N) | Space O(N) */
 
- s = s.toLowerCase();
+const reverse = (s) => s
+ .split('')/* Time O(N) | Space O(N) */
+ .reverse()/* Time O(N) | Space O(N) */
+ .join('');/* Time O(N) | Space O(N) */
 
- return isValid(s);
+/**
+ * 2 Pointer | Midde Convergence
+ * Time O(N) | Space O(1)
+ * https://leetcode.com/problems/valid-palindrome/
+ * @param {string} s
+ * @return {boolean}
+ */
+var isPalindrome = function(s) {
+ if (!s.length) return true;
+
+ return isValid(s);/* Time O(N) */
 };
 
 const isValid = (s) => {
- let [left, right] = [0, s.length - 1];
+ let [ left, right ] =  [ 0, (s.length - 1) ];
 
- while (left < right) {
- while (left < right && isNonAlphaNumeric(s[left])) left++;
- while (left < right && isNonAlphaNumeric(s[right])) right--;
+ while (left < right) { /* Time O(N) */
+ [ left, right ] = moveToMid(s, left, right);/* Time O(N) */
 
- const isSame = s[left] === s[right];
- if (!isSame) return false;
+ const [ leftCode, rightCode ] = getCodes(s, left, right);
+
+ const isEqual = leftCode === rightCode;
+ if (!isEqual) return false;
 
- left++;
- right--;
+ left++; right--;
  }
 
  return true;
-};
+}
 
-const isNonAlphaNumeric = (char) => {
- const isNonAlpha = char < 'a' || 'z' < char; // a(97) - z(122)
- const isNonNumeric = char < '0' || '9' < char; // 0(48) - 9(57)
+const moveToMid = (s, left, right) => {
+ while ((left < right) && !isAlphaNumeric(s[left])) left++; /* Time O(N) */
+ while ((left < right) && !isAlphaNumeric(s[right])) right--;/* Time O(N) */
+
+ return [ left, right ];
+}
 
- return isNonAlpha && isNonNumeric;
-};
+const getCodes = (s, left, right) => [ getCode(s[left]), getCode(s[right]) ];
 
-/**
- * https://leetcode.com/problems/valid-palindrome/
- * Time O(N) | Space O(N)
- * @param {string} s
- * @return {boolean}
- */
-var isPalindrome = function(s) {
- if (!s.length) return true;
-
- s = s.toLowerCase();
- s = s.replace(/[^a-z0-9]/gi, '');
-
- let reversed = s.split('').reverse().join('');
+const getCode = (char) => char.toLowerCase().charCodeAt(0);
+
+const isAlphaNumeric = (char) => {
+ const code = getCode(char);
 
- return reversed === s;
+ const [ a, z ] = [ 97, 122 ];
+ const isAlpha = (a <= code) && (code <= z);
+
+ const [ zero, nine ] = [ 48, 57 ];
+ const isNumeric = (zero <= code) && (code <= nine);
+
+ return isAlpha || isNumeric;
 };