From bc160b43afd0aeeff9fa5daa874e9966bbf667a3 Mon Sep 17 00:00:00 2001
From: Jc Calayag <138150245+Jccqt@users.noreply.github.com>
Date: Sat, 12 Jul 2025 06:49:08 +0800
Subject: [PATCH] Add Valid Parentheses Checker algorithm

---
 .../Strings/ValidParenthesesTests.cs          | 31 +++++++++++
 Algorithms/Strings/ValidParentheses.cs        | 52 +++++++++++++++++++
 README.md                                     |  1 +
 3 files changed, 84 insertions(+)
 create mode 100644 Algorithms.Tests/Strings/ValidParenthesesTests.cs
 create mode 100644 Algorithms/Strings/ValidParentheses.cs

diff --git a/Algorithms.Tests/Strings/ValidParenthesesTests.cs b/Algorithms.Tests/Strings/ValidParenthesesTests.cs
new file mode 100644
index 00000000..420754fb
--- /dev/null
+++ b/Algorithms.Tests/Strings/ValidParenthesesTests.cs
@@ -0,0 +1,31 @@
+using System;
+using NUnit.Framework;
+using Algorithms.Strings;
+
+namespace Algorithms.Tests.Strings
+{
+    public static class ValidParenthesesTests
+    {
+        [TestCase("([{}])")]
+        public static void IsValidParentheses_TrueExpected(string parentheses)
+        {
+            // Arrange
+            // Act
+            var isValidParentheses = ValidParentheses.IsValidParentheses(parentheses);
+
+            // Assert
+            Assert.That(isValidParentheses, Is.True);
+        }
+
+        [TestCase("([)[}")]
+        public static void IsValidParentheses_FalseExpected(string parentheses)
+        {
+            // Arrange
+            // Act
+            var isValidParentheses = ValidParentheses.IsValidParentheses(parentheses);
+
+            // Assert
+            Assert.That(isValidParentheses, Is.False);
+        }
+    }
+}
diff --git a/Algorithms/Strings/ValidParentheses.cs b/Algorithms/Strings/ValidParentheses.cs
new file mode 100644
index 00000000..b5616343
--- /dev/null
+++ b/Algorithms/Strings/ValidParentheses.cs
@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+
+namespace Algorithms.Strings
+{
+    /// <summary>
+    ///     This is a class for checking if the parentheses is valid.
+    ///     A valid parentheses should have opening brace and closing brace.
+    /// </summary>
+    public class ValidParentheses
+    {
+        /// <summary>
+        ///     Function to check if the parentheses is valid.
+        /// </summary>
+        /// <param name="parentheses">String to be checked.</param>
+        public static bool IsValidParentheses(string parentheses)
+        {
+            if (parentheses.Length % 2 != 0)
+            {
+                return false;
+            }
+
+            Stack<char> stack = new Stack<char>();
+
+            foreach(char c in parentheses.ToCharArray())
+            {
+                if(c == '(' || c == '{' || c == '[')
+                {
+                    stack.Push(c);
+                }
+                else if (c == ')' && stack.Count != 0 && stack.Peek() == '(')
+                {
+                    stack.Pop();
+                }
+                else if (c == '}' && stack.Count != 0 && stack.Peek() == '{')
+                {
+                    stack.Pop();
+                }
+                else if (c == ']' && stack.Count != 0 && stack.Peek() == '[')
+                {
+                    stack.Pop();
+                }
+                else
+                {
+                    stack.Push(c);
+                }
+            }
+
+            return stack.Count == 0;
+        }
+    }
+}
diff --git a/README.md b/README.md
index b9933f9f..d57f3446 100644
--- a/README.md
+++ b/README.md
@@ -213,6 +213,7 @@ find more than one implementation for the same objective but using different alg
     * [Longest Consecutive Character](./Algorithms/Strings/GeneralStringAlgorithms.cs)
     * [Palindrome Checker](./Algorithms/Strings/Palindrome.cs)
     * [Get all permutations of a string](./Algorithms/Strings/Permutation.cs)
+    * [Valid Parentheses Checker](./Algorithms/Strings/ValidParentheses.cs)
   * [Other](./Algorithms/Other)
     * [Fermat Prime Checker](./Algorithms/Other/FermatPrimeChecker.cs)
     * [Sieve of Eratosthenes](./Algorithms/Other/SieveOfEratosthenes.cs)