add initial data

0020-valid-parentheses/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "leetcode"
+version = "0.1.0"

0020-valid-parentheses/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "leetcode"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

0020-valid-parentheses/src/main.rs

@@ -0,0 +1,64 @@
+fn main() {
+    println!("Hello, world!");
+}
+
+pub fn is_valid(s: String) -> bool {
+    helper(s).unwrap_or(false)
+}
+
+fn helper(s: String) -> Option<bool> {
+    let mut stack = vec![];
+
+    for c in s.chars() {
+        if ['(', '[', '{'].contains(&c) {
+            stack.push(c);
+        }
+        if [')', ']', '}'].contains(&c) {
+            if matches(c, *stack.last()?) {
+                stack.pop();
+            } else {
+                return Some(false);
+            }
+        }
+    }
+    Some(stack.is_empty())
+}
+
+fn matches(current: char, previous: char) -> bool {
+    match current {
+        ')' => previous == '(',
+        ']' => previous == '[',
+        '}' => previous == '{',
+        _ => unreachable!(),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::is_valid;
+
+    #[test]
+    fn test_1() {
+        assert!(is_valid("()".to_string()))
+    }
+
+    #[test]
+    fn test_2() {
+        assert!(is_valid("()[]{}".to_string()))
+    }
+
+    #[test]
+    fn test_3() {
+        assert!(!is_valid("(]".to_string()))
+    }
+
+    #[test]
+    fn test_4() {
+        assert!(is_valid("([])".to_string()))
+    }
+
+    #[test]
+    fn test_5() {
+        assert!(!is_valid("([)]".to_string()))
+    }
+}