1. Valid Parentheses

Author: Sunjae95

valid-parentheses/sunjae95.js

@@ -0,0 +1,32 @@
+/**
+ * @description
+ * brainstorming:
+ * stack
+ *
+ * n: length of s
+ * time complexity: O(n)
+ * space complexity: O(n)
+ */
+var isValid = function (s) {
+  const stack = [];
+
+  for (let i = 0; i < s.length; i++) {
+    if (s[i] === "(" || s[i] === "{" || s[i] === "[") {
+      stack.push(s[i]);
+      continue;
+    }
+
+    const top = stack.length ? stack[stack.length - 1] : null;
+    if (top === null) return false;
+
+    if (
+      (top === "(" && s[i] === ")") ||
+      (top === "{" && s[i] === "}") ||
+      (top === "[" && s[i] === "]")
+    ) {
+      stack.pop();
+    } else return false;
+  }
+
+  return !stack.length;
+};