415. Add Strings

Given two non-negative numbers num1 and num2 represented as string, return the sum of num1 and num2.

Note:

The length of both num1 and num2 is < 5100.
Both num1 and num2 contains only digits 0-9.
Both num1 and num2 does not contain any leading zero.
You must not use any built-in BigInteger library or convert the inputs to integer directly.

#include<iostream>#include<string>#include<vector>#include<algorithm>using namespace std;class Solution {public:    string addStrings(string num1, string num2)     {        int x=num1.size(),            y=num2.size(),            i,carry,temp;        vector<int>ret;        if(x==0&&y==0)            return "";        reverse(num1.begin(),num1.end());        reverse(num2.begin(),num2.end());        carry=0;        for(i=0;i<x&&i<y;i++)        {            temp=(num1[i]-'0')+(num2[i]-'0')+carry;            carry=temp/10;            ret.push_back(temp%10);        }        while(i<x)        {            temp=num1[i]-'0'+carry;            carry=temp/10;            ret.push_back(temp%10);            i++;        }        while(i<y)        {            temp=num2[i]-'0'+carry;            carry=temp/10;            ret.push_back(temp%10);            i++;        }        if(carry>0)            ret.push_back(carry);        string s;        for(i=ret.size()-1;i>=0;i--)//将整数数组转化为字符串        {            char c=ret[i]+'0';            s=s+c;        }        return s;    }};int main(){    string num1,num2;    cin>>num1>>num2;    string result;    Solution solve;    cout<<solve.addStrings(num1,num2)<<endl;    return 0;}