Google·Software Engineer·Technical Phone Screen
Jun 2026
Google SWE coding round, one problem the whole session. Subtraction on big number strings, no BigInteger allowed. Felt manageable at first but the edge cases piled up fast.
- Given two non-negative integers as strings, compute their difference (num1 minus num2) and return the result as a string. You cannot convert the inputs to a native big integer type; you have to do the subtraction digit by digit. The result can be negative, and leading zeros should be stripped from the output.
“I started okay, figured out I needed to handle the sign first by comparing which string was larger, then do the actual subtraction on the bigger minus the smaller.” The rest of the author's notes on Software Engineer interview at Google, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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