From a2ef39abaf763d81fc7cee30a938949d13882897 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Mon, 17 Aug 2020 20:49:29 +0800
Subject: import(solutions): Add problem 20 .

---
 works/solutions/cpp/20.cpp | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 works/solutions/cpp/20.cpp

(limited to 'works/solutions/cpp/20.cpp')

diff --git a/works/solutions/cpp/20.cpp b/works/solutions/cpp/20.cpp
new file mode 100644
index 0000000..e994e96
--- /dev/null
+++ b/works/solutions/cpp/20.cpp
@@ -0,0 +1,55 @@
+#include <string>
+
+using std::string;
+
+#include <stack>
+
+class Solution
+{
+public:
+    inline static char get_companion(char c)
+    {
+        switch (c)
+        {
+        case ')':
+            return '(';
+        case ']':
+            return '[';
+        default:
+            return '{';
+        }
+    }
+
+    bool isValid(string s)
+    {
+        std::stack<char> stack;
+
+        for (const auto c : s)
+        {
+            switch (c)
+            {
+            case '(':
+            case '[':
+            case '{':
+            {
+                stack.push(c);
+                break;
+            }
+            case ')':
+            case ']':
+            default:
+            {
+                if (stack.empty())
+                    return false;
+                const auto top = stack.top();
+                const char companion = get_companion(c);
+                if (top != companion)
+                    return false;
+                stack.pop();
+            }
+            }
+        }
+
+        return stack.empty();
+    }
+};
-- 
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