<仅是自己做笔记。。。系列-12>输入一个表示整数的字符串，把该字符串转换成整数并输出。

#include <iostream>
using namespace std;
long str2Int(char*str)
{
int i = 0,flag = 1;
long result = 0;
if(str[0] == '-')
{
i = 1;
flag = -1;
}
else if(str[0] == '+')
{
i = 1;
}
for(; str[i] != '\0';i ++)
{
if(str[i] >= '0' && str[i] <= '9')
{
result *= 10;
result += str[i] - '0';
if(result < 0)
{
cout << "overflow" << endl;
return -1;
}
}
else
{
cout << "error" <<endl;
return -1;
}
}
cout <<flag*result << endl;
return flag*result;
}

int main(int argc, char *argv[])
{
str2Int("012347454881240");
return 0;
}