feat: add [20] 有效的括号

Author: pdsuwwz

20.有效的括号.ts

@@ -0,0 +1,34 @@
+/*
+ * @lc app=leetcode.cn id=20 lang=typescript
+ *
+ * [20] 有效的括号
+ */
+
+// @lc code=start
+function isValid(str: string): boolean {
+  const leftMapping = {
+    '(': ')',
+    '{': '}',
+    '[': ']',
+    ')': '(',
+    '}': '{',
+    ']': '['
+  }
+  const stack: Array<string> = []
+  for (let i = 0; i < str.length; i++) {
+    const chars = str[i]
+    if (['(', '{', '['].includes(chars)) {
+      stack.push(chars)
+      continue
+    }
+    if (stack[stack.length - 1] === leftMapping[chars]) {
+      stack.pop()
+    } else {
+      return false
+    }
+  }
+
+  return stack.length === 0
+};
+// @lc code=end
+