LeetCode 8. String to Integer (atoi)

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.

程序代码：

int myAtoi(char* str) {    char *p = str;    int flag = 1;    while(*p==' ')        p++;    if(*p=='-'||*p=='+')    {        flag = 1-2*(*p=='-');        p++;    }    int sum = 0;    while(*p>='0'&&*p<='9')    {        if(sum>INT_MAX/10||(sum==INT_MAX/10&&*p-'0'>7))        {            if(flag==-1)    return INT_MIN;            else        return INT_MAX;        }        sum = sum *10 +*p-'0';        p++;    }    return sum*flag;}