剑指offer49 把字符串转换成整数

这个代码会报错

class Solution {
public:
    enum status {kvalid = 0,kinvalid};
    int now_status = kvalid;
    int StrToInt(string str) {
        now_status = kinvalid;
        long long num = 0;
        int index = 0;
        bool minus = false;
        if(str.size() != 0 && str[index] != ''){
            if(str[index] == '+'){
                index++;
            }
            else if(str[index] == '-'){
                minus = true;
                index++;
            }
            if(str[index] != ''){
                num = StrToIntCore(str,minus,index);
            }            
        }
        return int(num);
    }
    long long StrToIntCore(string str,bool minus,int index){
        int length = str.size();
        long long num = 0;
        int flag = minus ? -1 : 1;
        for(;index < length;index++){
            if(str[index] >= '0' && str[index] <= '9'){
                num = num*10 + flag * (str[index]-'0');if(( num < 0x80000000) || ( num > 0x7FFFFFFF)){
                    num = 0;
                    break;
                }
            }
            else{
                num = 0;
                break;
            }
        }
        if(str[index] == ''){
            now_status = kvalid;
        }
        return num;
    }
};

修改为：

class Solution {
public:
    enum status {kvalid = 0,kinvalid};
    int now_status = kvalid;
    int StrToInt(string str) {
        now_status = kinvalid;
        long long num = 0;
        int index = 0;
        bool minus = false;
        if(str.size() != 0 && str[index] != ''){
            if(str[index] == '+'){
                index++;
            }
            else if(str[index] == '-'){
                minus = true;
                index++;
            }
            if(str[index] != ''){
                num = StrToIntCore(str,minus,index);
            }            
        }
        return int(num);
    }
    long long StrToIntCore(string str,bool minus,int index){
        int length = str.size();
        long long num = 0;
        int flag = minus ? -1 : 1;
        for(;index < length;index++){
            if(str[index] >= '0' && str[index] <= '9'){
                num = num*10 + flag * (str[index]-'0');
                int xxxx= 0x80000000;
                if(( num < xxxx) || ( num > 0x7FFFFFFF)){
                    num = 0;
                    break;
                }
            }
            else{
                num = 0;
                break;
            }
        }
        if(str[index] == ''){
            now_status = kvalid;
        }
        return num;
    }
};

或者修改为

class Solution {
public:
    enum status {kvalid = 0,kinvalid};
    int now_status = kvalid;
    int StrToInt(string str) {
        now_status = kinvalid;
        long long num = 0;
        int index = 0;
        bool minus = false;
        if(str.size() != 0 && str[index] != ''){
            if(str[index] == '+'){
                index++;
            }
            else if(str[index] == '-'){
                minus = true;
                index++;
            }
            if(str[index] != ''){
                num = StrToIntCore(str,minus,index);
            }            
        }
        return int(num);
    }
    long long StrToIntCore(string str,bool minus,int index){
        int length = str.size();
        long long num = 0;
        int flag = minus ? -1 : 1;
        for(;index < length;index++){
            if(str[index] >= '0' && str[index] <= '9'){
                num = num*10 + flag * (str[index]-'0');
                if(( num < （signed int）0x80000000) || ( num > 0x7FFFFFFF)){
                    num = 0;
                    break;
                }
            }
            else{
                num = 0;
                break;
            }
        }
        if(str[index] == ''){
            now_status = kvalid;
        }
        return num;
    }
};