using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

    /*

    Write a function to identify if a given string of brackets is well formed

       Bracket types are { }, [ ], ( )

       Examples:

        Valid - ( [ ] )

        Valid - ( ) { }

        Invalid - { ( }

        Invalid - { {

    */

        var valids = new List<string>(){

            "( [ ] )",

            "( ) { }"

        };

        var invalids = new List<string>(){

            "{ ( }",

            "{ {"

        };

        foreach (var v in valids){

            var x = Program.isWellFormed(v);

            Console.Out.WriteLine("Valid string has result of: " + x);

        }

​

        foreach (var v in invalids)

        {

            var x = isWellFormed(v);

            Console.Out.WriteLine("Invalid string has result of: " + x);

        }

    }

    public static bool isWellFormed(string s){

        var lefts = new Stack<char>();

​

        foreach (var c in s.ToCharArray())

        {

            if (IsLeft(c)){

                lefts.Push(c);

            }

            else if (IsRight(c)){

​

                if (lefts.Count == 0){

                    return false;

                }

                var l = lefts.Pop();

                return isPaired(l, c);

            }

​

            // otherwise skip   

        }

        return lefts.Count == 0;

    }

​

    public static bool isPaired(char left, char right){

        List<char> lefts = new List<char>(){ '(', '[', '{' };

        List<char> rights = new List<char>() { ')', ']', '}' };

​

        for (int i=0; i<lefts.Count; i++){

            if (left == lefts[i]){

                return right == rights[i];

            }

        }

        return false;

    }

​

    public static bool IsLeft(char c){

        List<char> lefts = new List<char>(){ '(', '[', '{' };

        return lefts.Contains(c);

    }

​

    public static bool IsRight(char c)

    {

        List<char> rights = new List<char>() { ')', ']', '}' };

        return rights.Contains(c);

    }

}