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10. Same Tree

easyAsked at Indeed

Check if two binary trees are structurally and value-wise identical — Indeed uses it as a building block for duplicate-posting tree comparison.

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 tree. Two trees are the same when their structure is identical and corresponding nodes have equal values.

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 both trees to strings then compare.

Time
O(n)
Space
O(n)
const serial = (n) => n ? `${n.val},${serial(n.left)},${serial(n.right)}` : '#';
return serial(p) === serial(q);

Tradeoff:

2. Synchronous recursion

Compare current nodes, then recurse on both pairs of children.

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:

Indeed-specific tips

Indeed wants the early-exit short-circuit explained out loud — they apply the same logic when comparing canonical job-posting trees for dedup.

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Output

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