valid parentheses

Author: YuuuuuuYu

valid-parentheses/YuuuuuuYu.java

@@ -0,0 +1,33 @@
+/**
+ * Runtime: 4ms
+ * Time Complexity: O(n)
+ *
+ * Memory: 42.94MB
+ * Space Complexity: O(n)
+ *
+ * Approach: 스택 사용
+ * - 열린 괄호를 푸시하면서 닫힌 괄호가 나올 때마다 스택에서 팝하여 짝이 맞는지 확인
+ */
+class Solution {
+    public boolean isValid(String s) {
+        if (s.length()%2 == 1) return false;
+
+        Stack<Character> stack = new Stack<>();
+        Map<Character, Character> map = new HashMap<>();
+        map.put('(', ')');
+        map.put('{', '}');
+        map.put('[', ']');
+
+        for (char ch: s.toCharArray()) {
+            if (map.containsKey(ch)) {
+                stack.push(ch);
+            } else if (")}]".indexOf(ch) != -1) {
+                if (stack.isEmpty() || ch != map.get(stack.pop())) {
+                    return false;
+                }
+            }
+        }
+
+        return stack.isEmpty();
+    }
+}