Evaluate Boolean Binary Tree

LeetCode 2331 • Easy • Trees

Input: root = [2,1,3,null,null,0,1] → Output: true
Leaves are 0/1. Non-leaves: 2 = OR, 3 = AND. Post-order: evaluate children, then combine.

TimeO(n)visit each node

SpaceO(h)recursion depth

Call stack: []Result: —

Current

On call stack

Evaluated

Call

empty

Speed:

Ready

Press Play. Post-order DFS: leaf → bool; OR (2) / AND (3) combine children.

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Practice until you don't need to look. Post-order: leaves first, then OR/AND.

═══ EVALUATE BOOLEAN BINARY TREE ═══

PATTERN ▸ Post-order DFS O(n) · O(h)

① LEAF

if not root.left: return root.val == 1

② RECURSE

L = evaluate(left); R = evaluate(right)

③ COMBINE

val==2 → L or R else L and R

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