# { Balanced Brackets }

Solving the Programming Challenge

# Balanced Brackets

## Problem

A bracket is considered to be any one of the following characters: (, ), {, }, [, or ].

Two brackets are considered to be a matched pair if the an opening bracket (i.e., (, [, or {) occurs to the left of a closing bracket (i.e., ), ], or }) of the exact same type. There are three types of matched pairs of brackets: [], {}, and ().

A matching pair of brackets is not balanced if the set of brackets it encloses are not matched. For example, {[(])} is not balanced because the contents in between { and } are not balanced. The pair of square brackets encloses a single, unbalanced opening bracket, (, and the pair of parentheses encloses a single, unbalanced closing square bracket, ].

By this logic, we say a sequence of brackets is balanced if the following conditions are met:

It contains no unmatched brackets. The subset of brackets enclosed within the confines of a matched pair of brackets is also a matched pair of brackets. Given strings of brackets, determine whether each sequence of brackets is balanced. If a string is balanced, return YES. Otherwise, return NO.

## My Solution

I’m providing the solution for Python and JS, please leave on the comments if you found a better way.

``````def isBalanced(s):
openers = ['(', '{', '[']
closers = {
')': '(',
'}': '{',
']': '['
}
bracket_stack = []
for c in s:
if c in openers:
bracket_stack.append(c)
elif c in closers:
if len(bracket_stack) == 0:
return 'NO'

if bracket_stack.pop() != closers[c]:
return 'NO'

if len(bracket_stack) > 0:
return 'NO'

return 'YES'
``````
``````function isBalanced(s) {
const openers = ['(', '{', '['];
const closers = {
')': '(',
'}': '{',
']': '['
};
const bracket_stack = [];

for (let i=0; i<s.length; i++) {
const c = s.charAt(i);
if (openers.includes(c)) {
bracket_stack.push(c);
} else if (closers[c]) {
if (bracket_stack.length == 0) {
return 'NO';
}

if (bracket_stack.pop() !== closers[c]) {
return 'NO';
}
}
}

if (bracket_stack.length > 0) {
return 'NO';
}

return 'YES';
}
``````