From 35cdc15fc942661cbcf9ebf5fe8152adc3cd2cad Mon Sep 17 00:00:00 2001
From: Manuel Pineda <manuelpineda@google.com>
Date: Wed, 20 Jan 2021 14:05:17 +0100
Subject: [PATCH] [LeetCode] Add January 20.

---
 solved/LeetCode/Challenges/2020/January/20.kt | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 solved/LeetCode/Challenges/2020/January/20.kt

diff --git a/solved/LeetCode/Challenges/2020/January/20.kt b/solved/LeetCode/Challenges/2020/January/20.kt
new file mode 100644
index 00000000..84ac40e2
--- /dev/null
+++ b/solved/LeetCode/Challenges/2020/January/20.kt
@@ -0,0 +1,24 @@
+class Solution {
+  var state = 0
+  val matcher = mapOf(
+    '(' to ')',
+    '{' to '}',
+    '[' to ']'
+  )
+  
+  fun isValid(s: String): Boolean {
+    return parse(s) && state == s.length
+  }
+  
+  fun parse(s: String): Boolean {
+    if (state >= s.length) return true
+    val cur = s[state]
+    if (cur !in matcher.keys) return true
+    state++
+    val next = parse(s)
+    if (!next || state >= s.length) return false
+    if (matcher[cur] != s[state]) return false;
+    state++
+    return parse(s)
+  }
+}