不使用库函数，将char *→int

#include <stdio.h>

int str2int(const char *str)
{
    int total = 0;
    int sign = 1;
    const char *pStr = str;

    /* skip space */
    while(*pStr == ' ')
    {
        ++pStr;
    }

    /* save sign */
    if(*pStr == '-' || *pStr == '+')
    {
        if(*pStr == '-')
        {
            sign = -1;
        }

        ++pStr;
    }

    /* skip '0' */
    while(*pStr == '0')
    {
        ++pStr;
    }

    while(*pStr != '\0')
    {
        if(*pStr >= '0' && *pStr <= '9')
        {
            total = 10 * total + (*pStr - '0');
        }

        ++pStr;
    }

    if(sign == -1)
    {
        total = - total;
    }

    return total;
}

int main()
{
    int ret = 0;

    ret = str2int("-12345");
    ret = str2int("+12345");
    ret = str2int("012345");
    ret = str2int(" 12345");
    ret = str2int("1234b");
    ret = str2int("12b45");

    return 0;
}