Javascript - queue in 10 lines
\nvar isSymmetric = function(root) {\n  const q = [root, root];\n  while (q.length) {\n    const [l, r] = [q.shift(), q.shift()];\n    if (!l && !r) continue;\n
```\nvar isSymmetric = function(root) {\n  const q = [root, root];\n  while (q.length) {\n    const [l, r] = [q.shift(), q.shift()];\n    if (!l && !r) continue;\n    if (!!l !== !!r || l.val !== r.val) return false;\n    q.push(l.left, r.right, l.right, r.left);\n  }\n  \n  return true;\n};\n\n```
['Queue', 'JavaScript']