Leetcode 415 Add Strings

Leetcode 415 Add Strings

class Solution {public:    string addStrings(string num1, string num2) {        //模拟进位加法        int carry = 0;//carry bit        string sumString;        int size1 = num1.size();        int size2 = num2.size();        int i = 1;        while(size1 - i >= 0 || size2 - i >= 0)        {            int bitSum = 0;            if(size1 - i >= 0)                bitSum += num1[size1 - i] - '0';            if(size2 - i >= 0)                bitSum += num2[size2 - i] - '0';            sumString += (bitSum + carry) % 10 +'0';//ATTENTION +'0'            carry = (bitSum + carry) / 10;            i ++;        }        if(carry)            sumString += '1';        reverse(sumString.begin(),sumString.end());        return sumString;    }};