freeCodeCamp/curriculum/challenges/en/08-coding-interview-prep/rosetta-code/balanced-brackets.en.md

title, id, challengeType

title	id	challengeType
Balanced brackets	594dc6c729e5700999302b45	5

Description

Determine whether a generated string of brackets is balanced; that is, whether it consists entirely of pairs of opening/closing brackets (in that order), none of which mis-nest.

Examples:

(empty) true

[] true

][ false

[][] true

][][ false

[]][[] false

[[[[]]]] true

Instructions

Tests

- text: <code>isBalanced</code> is a function.
  testString: 'assert(typeof isBalanced === ''function'', ''<code>isBalanced</code> is a function.'');'
- text: '<code>isBalanced("[]")</code> should return true.'
  testString: 'assert(isBalanced(testCases[0]), ''<code>isBalanced("[]")</code> should return true.'');'
- text: '<code>isBalanced("]][[[][][][]][")</code> should return false.'
  testString: 'assert(!isBalanced(testCases[1]), ''<code>isBalanced("]][[[][][][]][")</code> should return false.'');'
- text: '<code>isBalanced("[][[[[][][[[]]]]]]")</code> should return true.'
  testString: 'assert(isBalanced(testCases[2]), ''<code>isBalanced("[][[[[][][[[]]]]]]")</code> should return true.'');'
- text: '<code>isBalanced("][")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[3]), ''<code>isBalanced("][")</code> should return true.'');'
- text: '<code>isBalanced("[[[]]]][[]")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[4]), ''<code>isBalanced("[[[]]]][[]")</code> should return true.'');'
- text: '<code>isBalanced("][[]")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[5]), ''<code>isBalanced("][[]")</code> should return true.'');'
- text: '<code>isBalanced("][[][]][[[]]")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[6]), ''<code>isBalanced("][[][]][[[]]")</code> should return true.'');'
- text: '<code>isBalanced("[[][]]][")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[7]), ''<code>isBalanced("[[][]]][")</code> should return true.'');'
- text: '<code>isBalanced("[[[]]][[]]]][][[")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[8]), ''<code>isBalanced("[[[]]][[]]]][][[")</code> should return true.'');'
- text: '<code>isBalanced("[]][[]]][[[[][]]")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[9]), ''<code>isBalanced("[]][[]]][[[[][]]")</code> should return true.'');'
- text: '<code>isBalanced("][]][[][")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[10]), ''<code>isBalanced("][]][[][")</code> should return true.'');'
- text: '<code>isBalanced("[[]][[][]]")</code> should return true.'
  testString: 'assert(isBalanced(testCases[11]), ''<code>isBalanced("[[]][[][]]")</code> should return true.'');'
- text: '<code>isBalanced("[[]]")</code> should return true.'
  testString: 'assert(isBalanced(testCases[12]), ''<code>isBalanced("[[]]")</code> should return true.'');'
- text: '<code>isBalanced("]][]][[]][[[")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[13]), ''<code>isBalanced("]][]][[]][[[")</code> should return true.'');'
- text: '<code>isBalanced("][]][][[")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[14]), ''<code>isBalanced("][]][][[")</code> should return true.'');'
- text: '<code>isBalanced("][][")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[15]), ''<code>isBalanced("][][")</code> should return true.'');'
- text: '<code>isBalanced("[[]]][][][[]][")</code> should return true.'
  testString: 'assert(!isBalanced(testCases[16]), ''<code>isBalanced("[[]]][][][[]][")</code> should return true.'');'
- text: <code>isBalanced("")</code> should return true.
  testString: 'assert(isBalanced(testCases[17]), ''<code>isBalanced("")</code> should return true.'');'

Challenge Seed

function isBalanced (str) {
  // Good luck!
  return true;
}

After Test

console.info('after the test');

Solution

function isBalanced (str) {
  if (str === '') return true;
  let a = str;
  let b;
  do {
    b = a;
    a = a.replace(/\[\]/g, '');
  } while (a !== b);
  return !a;
}