The zero case and positive case I got through fine.
Clarify that the problem requires converting a 32-bit signed integer to its hexadecimal representation using two's complement for negatives, with no leading zeros and lowercase letters. Propose a bitwise approach that processes the integer in 4-bit chunks, using a lookup table for hex digits, and handle the special case of zero. Discuss trade-offs between bitwise manipulation and using built-in formatting, emphasizing correctness and efficiency.
Pro tip: Mention that you would avoid built-in functions like sprintf or Integer.toHexString to demonstrate low-level understanding, but acknowledge their existence and when they might be appropriate. Also, explicitly handle the edge case of zero to avoid returning an empty string.
Confirm that the input is a 32-bit signed integer, output should be lowercase hex without leading zeros, and negative numbers use two's complement. Identify edge cases: zero, negative numbers, and the minimum integer (-2^31).
Decide between bitwise manipulation (masking 4 bits at a time) and using built-in conversion. For an interview, prefer bitwise to show understanding, but mention built-in as a trade-off.
Use a loop to extract 4 bits at a time from the integer, map each nibble to a hex character via a lookup table, and build the string. For negative numbers, treat the integer as unsigned by using logical shifts or masking.
Skip leading zeros by not appending until a non-zero nibble is found, but ensure that zero returns '0'. Alternatively, build the string and strip leading zeros, handling the empty case.
Walk through test cases: 0, positive numbers, negative numbers, and -2^31. Discuss time/space complexity (O(1) since fixed 32 bits) and trade-offs between manual bitwise and built-in methods.
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