diff --git a/678-valid-parenthesis-string/driver.cpp b/678-valid-parenthesis-string/driver.cpp
new file mode 100644
index 0000000..0a91eda
--- /dev/null
+++ b/678-valid-parenthesis-string/driver.cpp
@@ -0,0 +1,10 @@
+#include "soln.hpp"
+
+int main()
+{
+	string s = "((**)((()))";
+	bool answer = true;
+	Solution soln;
+	cout << "Validated parenthesis string correctly? " << soln.test(s, answer) << endl;
+	return 0;
+}
\ No newline at end of file
diff --git a/678-valid-parenthesis-string/soln.cpp b/678-valid-parenthesis-string/soln.cpp
new file mode 100644
index 0000000..f761129
--- /dev/null
+++ b/678-valid-parenthesis-string/soln.cpp
@@ -0,0 +1,33 @@
+#include "soln.hpp"
+
+bool Solution::checkValidString(string s)
+{
+	int min_open = 0, max_open = 0;
+	for (int i = 0; i < s.length(); i++)
+	{
+		if (s[i] == '(')
+		{
+			min_open++;
+			max_open++;
+		}
+		else if (s[i] == ')')
+		{
+			min_open--;
+			max_open--;
+		}
+		else
+		{
+			min_open--;
+			max_open++;
+		}
+		if (max_open < 0)
+			break;
+		min_open = max(min_open, 0);
+	}
+	return min_open == 0;
+}
+
+bool Solution::test(string s, bool answer)
+{
+	return checkValidString(s) == answer;
+}
\ No newline at end of file
diff --git a/678-valid-parenthesis-string/soln.hpp b/678-valid-parenthesis-string/soln.hpp
new file mode 100644
index 0000000..ba07184
--- /dev/null
+++ b/678-valid-parenthesis-string/soln.hpp
@@ -0,0 +1,8 @@
+#include <bits/stdc++.h>
+using namespace std;
+class Solution
+{
+public:
+	bool checkValidString(string s);
+	bool test(string s, bool answer);
+};
\ No newline at end of file