solve: valid parentheses

Author: JustHm

valid-parentheses/JustHm.swift

@@ -0,0 +1,24 @@
+// time: O(n) space: O(n)
+class Solution {
+    func isValid(_ s: String) -> Bool {
+        var answer = [Character]()
+        for char in s {
+            if let recent = answer.last {
+                if char == ")" && recent == "(" {
+                    answer.removeLast()
+                    continue
+                }
+                else if char == "]" && recent == "[" {
+                    answer.removeLast()
+                    continue
+                }
+                else if char == "}" && recent == "{" {
+                    answer.removeLast()
+                    continue
+                }
+            }
+            answer.append(char)
+        }
+        return answer.isEmpty
+    }
+}