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.
别人的代码，很精简，值得学习。
1 class Solution { 2 public: 3 int atoi(const char *str) { 4 assert(str != NULL); 5 while(isspace(*str)) str++; // remove ‘ ‘ 6 7 int sign = (*str == ‘-‘) ? -1 : 1; 8 if (*str == ‘-‘ || *str == ‘+‘) // if can check one char 9 str++; 10 11 int ret = 0; 12 while(isdigit(*str)) // is digit 13 { 14 int digit = *str - ‘0‘; 15 16 if (INT_MAX / 10 >= ret) 17 ret *= 10; 18 else 19 return sign == -1 ? INT_MIN : INT_MAX; 20 21 if (INT_MAX - digit >= ret) 22 ret += digit; 23 else 24 return sign == -1 ? INT_MIN : INT_MAX; 25 26 str++; 27 } 28 29 return ret * sign; 30 } 31 };
[Leetcode] String to Integer (atoi),布布扣,bubuko.com
[Leetcode] String to Integer (atoi)
原文：http://www.cnblogs.com/easonliu/p/3631584.html