add Valid Palindrome solution

Author: HoonDongKang

valid-palindrome/HoonDongKang.ts

@@ -0,0 +1,49 @@
+/**
+ * [Problem]: [125] Valid Palindrome
+ *
+ * (https://leetcode.com/problems/valid-palindrome/description/)
+ */
+
+function isPalindrome(s: string): boolean {
+    // 시간복잡도: O(n)
+    // 공간복잡도: O(n)
+    function twoPointerFunc(s: string): boolean {
+        let stringArr: string[] = [...s.replace(/[^a-zA-Z0-9]/g, "")];
+        let left = 0;
+        let right = stringArr.length - 1;
+
+        while (left < right) {
+            if (stringArr[left].toLowerCase() === stringArr[right].toLowerCase()) {
+                left++;
+                right--;
+            } else {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    // 시간복잡도: O(n)
+    // 공간복잡도: O(1)
+    function optimizedTwoPointerFunc(s: string): boolean {
+        let left = 0;
+        let right = s.length - 1;
+
+        while (left < right) {
+            while (left < right && !isLetterOrDigit(s[left])) left++;
+            while (left < right && !isLetterOrDigit(s[right])) right--;
+
+            if (s[left].toLowerCase() !== s[right].toLowerCase()) return false;
+            left++;
+            right--;
+        }
+
+        return true;
+
+        function isLetterOrDigit(c: string): boolean {
+            return /[a-zA-Z0-9]/.test(c);
+        }
+    }
+    return optimizedTwoPointerFunc(s);
+}