String to Integer (atoi)

Implement a robust `atoi` that parses an optional sign, leading whitespace, and digit run, clamping to the 32-bit signed range. Bloomberg uses it as a phone-screen warm-up where overflow handling and a few targeted edge cases distinguish strong candidates. Requirements Implement a function: int myAtoi(String s) that behaves as follows: Skip leading whitespace. Read an optional '+' or '-' sign character. Read the digit run ('0'..'9') that follows. Stop at the first non-digit. Convert the digit run to a signed 32-bit integer with the sign from step 2. If the value exceeds the 32-bit signed range, clamp to INT_MAX (2^31 - 1) or INT_MIN (-2^31). If no digits were read after the optional sign, return 0. Follow-ups: How do you detect overflow before the multiplication overflows? Compare the accumulator against INT_MAX / 10 and the next digit against INT_MAX % 10. What about leading zeros, multiple signs ('--1'), or embedded whitespace ('1 23')? Walk through each case. Adapt to floats or scientific notation as a verbal follow-up. Examples '42' -> 42 ' -42' -> -42 '4193 with words'-> 4193 'words and 987' -> 0 '-91283472332' -> -2147483648 (clamped to INT_MIN) '+1' -> 1 '00000-42a1234' -> 0 (digits start, then '-' stops) Notes The cleanest implementation is a single pass with three phases: skip whitespace, read sign, read digits with overflow check on each iteration. Time O(n), space O(1). The overflow check is the single most-graded detail. The idiomatic Java / C++ approach: if (acc > INT_MAX / 10 || (acc == INT_MAX / 10 && digit > INT_MAX % 10)) return sign == 1 ? INT_MAX : INT_MIN; Doing it any other way (catching exceptions, casting through long) is acceptable but invites follow-up. Bloomberg interviewers often ask about negative-overflow asymmetry: INT_MIN has one more representable value than -INT_MAX. Handle by clamping after applying the sign, not before. Edge cases to enumerate before coding: leading whitespace only, sign with no digits, only a sign character, only digits, embedded sign mid-number, very long digit run that triggers overflow halfway. Preparation Re-derive the overflow check from INT_MAX = 2_147_483_647 on paper; don't rely on language built-ins. Implement once in Java (where int is 32-bit and overflow matters) and once in Python (where it doesn't, and you must check the bound manually); the second exposes whether you actually understand the constraint. Practice articulating the parsing rules out loud — Bloomberg explicitly grades whether the candidate enumerates ambiguities before writing code.