Code QuizAdvanced

Balanced Brackets with Stack & Map

Spot the subtle bug in a bracket-matching function using a stack and a hash map of pairs.

Codejavascript

function isBalanced(str) {
  const pairs = { ')': '(', ']': '[', '}': '{' };
  const stack = [];
  for (const ch of str) {
    if (ch === '(' || ch === '[' || ch === '{') {
      stack.push(ch);
    } else if (pairs[ch]) {
      if (stack.pop() !== pairs[ch]) return false;
    }
  }
  return true;
}

console.log(isBalanced("([)]"));  // false
console.log(isBalanced("((["));   // should be false

What is the bug in this bracket-matching code?

Next →Choosing the Right Data Structure