Whiteboard Problem Solving

Writing clean code on whiteboard, edge case handling, thinking aloud.

7 min readMastering Data Structures & Algorithms for Software Engineering InterviewsCode

Whiteboard Tips

Write large, legible — interviewer reads from distance
Leave space between lines for edits
Use descriptive names: left, right, maxSum not l, r, ms
Write function signature first: func solve(input []int) int
Draw diagram for data structures (tree, graph, array)
Box off sections: // Helper, // Main logic, // Tests

Code Structure

Goclean-whiteboard-template.go

31 linesLn 1, Col 1Go

Write time/space complexity comment. Handle edge cases first. Use clear loop structure. Extract helpers at bottom.

Edge Case Handling

Category	Cases to Check
Array/String	Empty, single element, all same, strictly increasing/decreasing
Tree/Graph	Null root, single node, skewed, cycles
Numbers	Zero, negative, overflow, INT_MIN/INT_MAX
DP	Empty input, n=1, n=2, all negative values
Two Pointers	Left=right, pointers cross, target not found

Thinking Aloud

Narrate every decision: 'I'll use sliding window because...', 'This edge case could break...', 'Time complexity is O(n) because...', 'Let me trace through example...'. If stuck: 'I'm considering two approaches...', 'Let me try a simpler version...', 'Can I assume input is sorted?'

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