feat: 125. Valid Palindrome

Author: HC-kang

contains-duplicate/HC-kang.rs

@@ -1,3 +1,8 @@
+/**
+ * https://leetcode.com/problems/contains-duplicate
+ * T.C. O(n)
+ * S.C. O(n)
+ */
 impl Solution {
     pub fn contains_duplicate(nums: Vec<i32>) -> bool {
         use std::collections::HashSet;

valid-palindrome/HC-kang.rs

@@ -0,0 +1,65 @@
+/**
+ * https://leetcode.com/problems/valid-palindrome
+ * T.C. O(n)
+ * S.C. O(n)
+ */
+impl Solution {
+    pub fn is_palindrome(s: String) -> bool {
+        let s: Vec<char> = s
+            .chars()
+            .filter(|c| c.is_alphanumeric())
+            .map(|c| c.to_ascii_lowercase())
+            .collect(); // T.C. O(n), S.C. O(n)
+            
+        let mut i = 0;
+        let mut j = s.len().saturating_sub(1);
+        
+        // T.C. O(n)
+        while i < j {
+            if s[i] != s[j] {
+                return false;
+            }
+            i += 1;
+            j -= 1;
+        }
+        true
+    }
+}
+
+/**
+ * 최적화
+ * T.C. O(n)
+ * S.C. O(1)
+ */
+impl Solution {
+    pub fn is_palindrome(s: String) -> bool {
+        let s = s.as_bytes();
+        let (mut left, mut right) = (0, s.len().saturating_sub(1));
+
+        while (left < right) {
+            while (left < right && !Self::is_alphanumeric(s[left])) {
+                left += 1;
+            }
+
+            while (left < right && !Self::is_alphanumeric(s[right])) {
+                right -= 1;
+            }
+
+            if left < right {
+                if s[left].to_ascii_lowercase() != s[right].to_ascii_lowercase() {
+                    return false;
+                }
+                left += 1;
+                right -= 1;
+            }
+        }
+
+        true
+    }
+
+    fn is_alphanumeric(c: u8) -> bool {
+        (c >= b'a' && c <= b'z') ||
+        (c >= b'A' && c <= b'Z') ||
+        (c >= b'0' && c <= b'9')
+    }
+}