feat: write charset based solution

Author: JCPedroza

src/interview-classics/is-palindrome/is-palindrome-while.js src/interview-classics/is-palindrome/is-palindrome-while-regex.js

@@ -2,7 +2,8 @@
 const charsToIgnore = /[-.,:;?!'"\s()]/
 
 /**
- * Checks if a string is a palindrome. Uses a while loop.
+ * Checks if a string is a palindrome. Uses a while loop and a regular
+ * expression.
  *
  * Time complexity: O(n)
  * Space complexity: O(1)
@@ -40,5 +41,5 @@ const isPalindrome = (str) => {
 
 module.exports = {
   fun: isPalindrome,
-  id: 'while-loop'
+  id: 'while-loop regex'
 }

src/interview-classics/is-palindrome/is-palindrome-while-set.js

@@ -0,0 +1,45 @@
+// Characters to remove from string in order to normalize it
+const charsToIgnore = new Set(['-', '.', ',', ':', ';', '?', '!', "'", '"',
+  '\n', ' ', '(', ')'])
+
+/**
+ * Checks if a string is a palindrome. Uses a while loop and set of characters.
+ *
+ * Time complexity: O(n)
+ * Space complexity: O(1)
+ *
+ * @param {string} str String to be checked.
+ * @returns {boolean} Whether the string is a palindrome.
+ */
+const isPalindrome = (str) => {
+  let leftIdx = 0
+  let rightIdx = str.length - 1
+
+  while (leftIdx < rightIdx) {
+    // Skip left characters that are in the ignore regex
+    while (charsToIgnore.has(str[leftIdx])) {
+      leftIdx++
+    }
+
+    // Skip right characters that are in the ignore regex
+    while (charsToIgnore.has(str[rightIdx])) {
+      rightIdx--
+    }
+
+    // Different characters, not a palindrome
+    if (str[leftIdx].toLowerCase() !== str[rightIdx].toLowerCase()) {
+      return false
+    }
+
+    // Equal characters, continue to next characters
+    leftIdx++
+    rightIdx--
+  }
+
+  return true
+}
+
+module.exports = {
+  fun: isPalindrome,
+  id: 'while-loop char-set'
+}

src/interview-classics/is-palindrome/is-palindrome.repo.js

@@ -1,6 +1,7 @@
 const solutions = [
   require('./is-palindrome-method'),
-  require('./is-palindrome-while')
+  require('./is-palindrome-while-regex'),
+  require('./is-palindrome-while-set')
 ]
 
 module.exports = solutions