Skip to main content

10. Same Tree

easyAsked at Spotify

Determine 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, return true if they are the same — same structure and same node values at every position.

Constraints

  • 0 <= nodes <= 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 both trees with nulls and string-compare

Time
O(n)
Space
O(n)
function ser(t){if(!t)return '#';return t.val+','+ser(t.left)+','+ser(t.right);}
return ser(p)===ser(q);

Tradeoff:

2. Recursive structural compare

Compare nodes pairwise, recursing on children. Short-circuit on any mismatch.

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

Tradeoff:

Spotify-specific tips

Spotify uses tree-equality for diffing playlist hierarchies between client and server, so emphasize early bail-out on first mismatch to mirror their sync logic.

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 Spotify interview questions under real-loop conditions with instant feedback on your reasoning, complexity claims, and code.

Practice these live with InterviewChamp.AI →