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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

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

const testCases = [
  '[]',
  ']][[[][][][]][',
  '[][[[[][][[[]]]]]]',
  '][',
  '[[[]]]][[]',
  '][[]',
  '][[][]][[[]]',
  '[[][]]][',
  '[[[]]][[]]]][][[',
  '[]][[]]][[[[][]]',
  '][]][[][',
  '[[]][[][]]',
  '[[]]',
  ']][]][[]][[[',
  '][]][][[',
  '][][',
  '[[]]][][][[]][',
  ''
];

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;
}

4.8 KiB Raw Blame History