LeetCode: Symmetric Tree Solution

Approach

Base cases:

• false
  when either left or right is null
• true
  when both left and right are null
• false
  when both values of left and right are not equal

Implementation

1var isSymmetric = function (root) {
2  if (!root) return true
3
4  const recursion = (left, right) => {
5    if ((!left && right) || (left && !right)) return false
6    if (!left && !right) return true
7    if (left.val !== right.val) return false
8    return (
9      recursion(left.left, right.right) && recursion(left.right, right.left)
10    )
11  }
12
13  return recursion(root.left, root.right)
14}

References

Original problem