ValidParentheses.cs

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 static 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)
            {
                switch (c)
                {
                    case '(':
                    case '{':
                    case '[':
                        stack.Push(c);
                        break;

                    case ')':
                        if (stack.Count == 0 || stack.Pop() != '(')
                        {
                            return false;
                        }

                        break;

                    case '}':
                        if (stack.Count == 0 || stack.Pop() != '{')
                        {
                            return false;
                        }

                        break;

                    case ']':
                        if (stack.Count == 0 || stack.Pop() != '[')
                        {
                            return false;
                        }

                        break;

                    default:
                        return false;
                }
            }

            return stack.Count == 0;
        }
    }
}