apexbortz / bracket-matcher

bracket matcher bonus assignment

Bracket Matcher

Let's say you're an SEI instructor at GA and you have a student who comes to you with broken code. It's really long, and while trying to find the error, you begin to suspect that there are mismatched parentheses, brackets, or braces. Wouldn't it be nice if you had a function that would take their code as input and return True or False depending on whether the code was valid? Let's make it happen!

Directions

• Fork and clone this repository
• Complete the requirements
• Push the answer to your Github and then make a pull request

Requirements

Write a Python function that takes a string input. This string represents code. It may have any number of characters in it, and the characters may be anything. For our purposes, we'll ignore anything that isn't one of the following: [, ], {, }, (, ). Your function definition looks like this:

def bracket_matcher(input):

The return value is a boolean. You should return True if the brackets are properly matched and nested, otherwise False.

HINT

This problem becomes remarkably easier to solve using a recent data structure we've learned in class. Hint, hint!

HELP! I need a bigger hint?

Alright - so, you want to keep track of (store in a data structure) opening brackets (or parentheses or braces) and then when you encounter a closing bracket, if it matches the previous opening bracket, great - keep going! But if it doesn't you can immediately return false. Whenever you encounter a closing bracket, it should match the type of the *most recently opened bracket*. In other words, if you encounter a `]`, then the last opening you should have seen would be a `[`. This is a LAST-IN-FIRST-OUT structure - so let's use a Stack!

Push opening brackets onto the stack, then pop them off and mack sure they match when you encounter a closing bracket.

At the very end, make sure that your data structure is empty! This will account for cases like ab[c where there is an opening bracket with no corresponding closing bracket.

Test Cases

Think you got it figured out? Run through these to make sure!

bracket_matcher('abc(123)')
# returns true

bracket_matcher('a[b]c(123')
# returns false -- missing closing parens

bracket_matcher('a[bc(123)]')
# returns true

bracket_matcher('a[bc(12]3)')
# returns false -- improperly nested

bracket_matcher('a{b}{c(1[2]3)}')
# returns true

bracket_matcher('a{b}{c(1}[2]3)')
# returns false -- improperly nested

bracket_matcher('()')
# returns true

bracket_matcher('[]]')
# returns false - no opening bracket to correspond with last character

bracket_matcher('abc123yay')
# returns true -- no brackets = correctly matched