非负大整数加法---网易校招附加题

网易2017校招内推附加题简单实现，大整数减法实现待续。。。：原题为实现一个大整数加减法的类。

string TwoBigInt(string str_bigNumber1,string str_bigNumber2){int length1 = str_bigNumber1.size();int length2 = str_bigNumber2.size();if(length1 > length2){str_bigNumber1.insert(0,length1 - length2,'0');}else if(length2 - length1){str_bigNumber1.insert(0,length2 - length1,'0');}string s = "";int cnt = 0;int i,j;for(i = length1 - 1; i >= 0; j--,i--){int sum = cnt + (bigNumber1[i] - '0') + (bigNumber2[j] - '0');int current = sum % 10;s = (current + '0') + s;cnt = sum / 10;}if(cnt == 1)s.insert(0,'1');return s;}