using System;

using System.Collections.Generic;

public class Program

{

    public static  Dictionary<char, char> _openCloseSymbols = new  Dictionary<char, char> ();

    public static void Main()

    {

        _openCloseSymbols.Add('(', ')');

        _openCloseSymbols.Add('[', ']');

        // MUST RETURN TRUE

        Console.WriteLine(Validate("(())"));

        Console.WriteLine(Validate("([])([()])"));

        Console.WriteLine(Validate("()()([])()()()([])()()()"));

        Console.WriteLine(Validate("()()([])()()()([])[]()()()"));

        // MUST RETURN FALSE

        Console.WriteLine(Validate("([)]"));

        Console.WriteLine(Validate("())"));

        Console.WriteLine(Validate(")(("));

    }

    public static bool Validate(string input)

    {

        if (string.IsNullOrEmpty(input))

        {

            return false;

        }

​

        var arr = input.ToCharArray();

        if (!_openCloseSymbols.ContainsKey(arr[0])) 

        {

            return false;

        }

​

        var stck = new Stack<char>();

        stck.Push(arr[0]);

        for (var i = 1; i < arr.Length; i++)

        {

            var curSym = arr[i]; 

            if (_openCloseSymbols.ContainsKey(curSym))

            {

                stck.Push(curSym);

            } 

            else if (!_openCloseSymbols.ContainsKey(curSym) && (stck.Count == 0 || _openCloseSymbols[stck.Pop()] != curSym))

            {

                return false;

            }

        }

        return true;

​

    }

}