Skip to main content

10. Same Tree

easyAsked at Quora

Check if two binary trees are structurally identical with equal values.

By Alex Chen, Founder, InterviewChamp.AI · Last verified

Problem

Given the roots of two binary trees p and q, determine if they are the same — same structure and same node values everywhere.

Constraints

  • 0 <= nodes per tree <= 100
  • -10^4 <= Node.val <= 10^4

Examples

Example 1

Input
p = [1,2,3], q = [1,2,3]
Output
true

Example 2

Input
p = [1,2], q = [1,null,2]
Output
false

Approaches

1. Serialize and compare

Serialize each tree to a string and compare.

Time
O(n)
Space
O(n)
const s = t => !t ? 'X' : `${t.val},${s(t.left)},${s(t.right)}`;
return s(p) === s(q);

Tradeoff:

2. Parallel recursion

Recurse into both trees together; short-circuit on mismatch.

Time
O(n)
Space
O(h)
function isSameTree(p, q) {
  if (!p && !q) return true;
  if (!p || !q) return false;
  return p.val === q.val
    && isSameTree(p.left, q.left)
    && isSameTree(p.right, q.right);
}

Tradeoff:

Quora-specific tips

Quora pairs tree-equality with dedup work — they collapse duplicate question subtrees by hashing structural fingerprints and only diff when the hashes collide.

Solve it now

Free. No sign-up. Python and JavaScript run instantly in your browser.

Output

Press Run or Cmd+Enter to execute

Practice these live with InterviewChamp.AI

Drill Same Tree and other Quora interview questions under real-loop conditions with instant feedback on your reasoning, complexity claims, and code.

Practice these live with InterviewChamp.AI →