Add Valid Parentheses Checker algorithm

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);
+        }
+    }
+}

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;
+        }
+    }
+}

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)