kyu6_valid_braces.py

"""
Write a function that takes a string of braces, and determines if the order of the braces is valid. It should return
true if the string is valid, and false if it's invalid;

This Kata is similar to the Valid Parentheses Kata, but introduces new characters: brackets [], and curly braces {};
Thanks to @arnedag for the idea!

All input strings will be nonempty, and will only consist of parentheses, brackets and curly braces: ()[]{};

What is considered Valid?
    A string of braces is considered valid if all braces are matched with the correct brace

Examples:
    "(){}[]"   =>  True
    "([{}])"   =>  True
    "(}"       =>  False
    "[(])"     =>  False
    "[({})](]" =>  False

https://www.codewars.com/kata/5277c8a221e209d3f6000b56

"""


def valid_braces(string):
    braces, accumulated = {'(': ')', '[': ']', '{': '}'}, []
    __match_current = lambda x: len(accumulated) == 0 or braces[accumulated.pop()] != x
    
    for item in string:
        if item in braces.keys():
            accumulated.append(item)
        elif __match_current(item):
                return False
    
    return len(accumulated) == 0