Add week 6 solutions: valid-parentheses

Author: gitsunmin

valid-parentheses/gitsunmin.ts

@@ -0,0 +1,25 @@
+/**
+ * https://leetcode.com/problems/valid-parentheses/
+ * time complexity : O(n)
+ * space complexity : O(n)
+ */
+
+type OpeningBracket = '(' | '[' | '{';
+type ClosingBracket = ')' | ']' | '}';
+
+const isEmpty = (stack: OpeningBracket[]): boolean => stack.length === 0;
+
+function isValid(s: string): boolean {
+    const m = new Map<string, ClosingBracket>([
+        ['(', ')'],
+        ['[', ']'],
+        ['{', '}']
+    ]);
+    const stack: OpeningBracket[] = [];
+
+    for (const c of s) {
+        if (m.has(c)) stack.push(c as OpeningBracket);
+        else if (isEmpty(stack) || c !== m.get(stack.pop() as OpeningBracket)) return false;
+    }
+    return isEmpty(stack);
+};