ITPEC FE Subject B April 2025 Question 9

Binary Tree Equality Check — fill in logical operators for a recursive same-tree comparison.

The function isSameTree(p, q) checks whether two binary trees are identical in both structure and values, using recursion.

Blank A — `and`:
if (p = undefined and q = undefined) → both nodes are absent, so the subtrees match at this point → return true.

Blank B — `or`:
if (p = undefined or q = undefined) → if we reach here, we know they're NOT both undefined (Blank A didn't trigger). So if either is undefined while the other isn't, the structures differ → return false.

Blank C — `and`:
return checkLeft and checkRight → the trees are identical only if both the left and right subtrees are identical.

Why not others:
- (a) or / and / and — Blank A with or would return true even when only one node is undefined, incorrectly treating mismatched structures as identical
- (b) and / or / or — Blank C with or would return true if only one subtree matches, allowing structurally different trees to pass
- (d) or / and / or — Blank A with or breaks the base case; Blank B with and only catches when both are undefined (already handled), missing the one-null case

Key rule: Base cases first — check both-null (and), then either-null (or), then compare values, then recurse on children requiring both to match (and).

AI-generated — may contain errors