8. String to Integer (atoi)

Loading Question ...

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

Update (2015-02-10):
The signature of the C++ function had been updated. If you still see your function signature accepts a const char * argument, please click the reload button to reset your code definition.

spoilers alert... click to show requirements for atoi.

Requirements for atoi:

The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.

The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.

If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.

If no valid conversion could be performed, a zero value is returned. If the correct value is out of the range of representable values, INT_MAX (2147483647) or INT_MIN (-2147483648) is returned.


Seen this question in a real interview before?  
Yes
No
When did you encounter this question?  
last week
last month
last 3 month
last 6 month
more than 6 months
other
Which company?  
Adobe
Aetion
Airbnb
Alibaba
Amazon
Apple
Baidu
Bloomberg
Cloudera
Coursera
Cryptic Studios
Dropbox
eBay
Epic Systems
Expedia
Facebook
Fallible
Games
Gilt Groupe
GoDaddy
Goo
Google
Hedvig
Houzz
Hulu
Indeed
Intuit
IXL
LinkedIn
LiveRamp
Lyft
MAQ Software
Mathworks
Microsoft
NetEase
Netsuite
Palantir
Palantir Technologies
Pinterest
Pocket Gems
Poynt
Pure
Pure Storage
Rackspace
Riot
Riot Games
Samsung
Snapchat
Square
Storage
Tencent
TinyCo
Twitter
Two Sigma
Uber
Valve
WAP
Works Applications
Yahoo
Yahoo!
Yelp
Zappos
Zenefits