class Solution {

public:

int StrToInt(string str) {

int len = str.size();

//如果字符串的第一个字符为'+'、'-'、数字才需要转换

if(len && (str[0] == '+' || str[0] == '-' || (str[0] >= '0' && str[0] <= '9')))

{

int ret = 0,flag;

if(str[0] == '-')

flag = -1;

else if(str[0] == '+')

flag = 1;

else

{

flag = 1;

ret = str[0]-'0';

}

string::iterator cur = str.begin() + 1;

//去掉前导0

while(cur < str.end() && *cur == '0')点此或手机扫描二维码查看代码编写过程

cur++;

while(cur < str.end())

{

if(*cur >= '0' && *cur <= '9')

{

ret = ret*10+*cur-'0';

cur++;

}

else

return 0;

}

return flag*ret;

}

return 0;

}

};