string--OJ1

链接: 例一

链接: 例er

class Solution {
public:
    int myAtoi(string str) {
        int sign = 1;
        int ret=0;
        int i=0;
        while(str[i]==' ')
        {
            i++;
        }
        if(str[i]=='+'||str[i]=='-')
        {
            if(str[i]=='-')
            sign*=-1;
            i++;
        }
        while(str[i]>='0'&&str[i]<='9')
        {
            int r=str[i] - '0';
            if(ret>INT_MAX/10||(ret==INT_MAX/10&&r>7))
            {
                return sign>0?INT_MAX:INT_MIN;
            }
            ret = ret * 10+r ;
            i++;
        }

        return ret*sign;
    }
};

class Solution {
public:
    string addStrings(string num1, string num2) {
        int sm=0,l1=num1.size(),l2=num2.size();
        string ans=""; 
        while(l1||l2||sm)
        {
            if(l1)
            sm+=num1[--l1]-'0';
            if(l2)
            sm+=num2[--l2]-'0';
            ans=char('0'+sm%10)+ans;
            sm/=10;
        }


        return ans;
    }
};