Valid Palindrome

suhwan2004/Valid Palindrome.js

@@ -0,0 +1,49 @@
+/*
+Time : O(N), Space : O(N)
+ALGO : two pointer
+DS : string
+Constraints
+ - 1 <= s.length <= 2 * 105
+ - s consists only of printable ASCII characters.
+Edge case : X
+*/
+
+var isPalindrome = function (s) {
+  let start = 0,
+    end = s.length - 1;
+
+  while (start !== end && start <= end) {
+    const sChar = changeLowerCase(s[start]);
+    const eChar = changeLowerCase(s[end]);
+
+    if (!checkValidChar(sChar)) {
+      start++;
+      continue;
+    } else if (!checkValidChar(eChar)) {
+      end--;
+      continue;
+    }
+
+    if (sChar !== eChar) {
+      return false;
+    } else {
+      start++;
+      end--;
+    }
+  }
+
+  return true;
+};
+
+const changeLowerCase = (c) => {
+  const charCd = c.charCodeAt();
+  if (charCd >= 65 && charCd <= 90) {
+    return c.toLowerCase();
+  }
+  return c;
+};
+
+const checkValidChar = (c) => {
+  const charCd = c.charCodeAt();
+  return (charCd >= 97 && charCd <= 122) || (charCd >= 48 && charCd <= 57);
+};